第三百二十九题：

class Solution {
public:
    int n, m;
    vector<vector<int>> f, w;
    int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
    int dp(int x, int y) {
        auto& v = f[x][y];
        if (v != -1) return v;
        v = 1;
        for (int i = 0; i < 4; i ++ ) {
            int a = x + dx[i], b = y + dy[i];
            if (a >= 0 && a < n && b >= 0 && b < m && w[x][y] < w[a][b])
                v = max(v, dp(a, b) + 1);
        }
        return v;
    }
    int longestIncreasingPath(vector<vector<int>>& matrix) {
        if (matrix.empty() || matrix[0].empty()) return 0;
        w = matrix;
        n = w.size(), m = w[0].size();
        f = vector<vector<int>>(n, vector<int>(m, -1));
        int res = 0;
        for (int i = 0; i < n; i ++ )
            for (int j = 0; j < m; j ++ )
                res = max(res, dp(i, j));
        return res;
    }
};

class Solution {
    public int[][] dirs = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
    public int rows, columns;

    public int longestIncreasingPath(int[][] matrix) {
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return 0;
        }
        rows = matrix.length;
        columns = matrix[0].length;
        int[][] outdegrees = new int[rows][columns];
        for (int i = 0; i < rows; ++i) {
            for (int j = 0; j < columns; ++j) {
                for (int[] dir : dirs) {
                    int newRow = i + dir[0], newColumn = j + dir[1];
                    if (newRow >= 0 && newRow < rows && newColumn >= 0 && newColumn < columns && matrix[newRow][newColumn] > matrix[i][j]) {
                        ++outdegrees[i][j];
                    }
                }
            }
        }
        Queue<int[]> queue = new LinkedList<int[]>();
        for (int i = 0; i < rows; ++i) {
            for (int j = 0; j < columns; ++j) {
                if (outdegrees[i][j] == 0) {
                    queue.offer(new int[]{i, j});
                }
            }
        }
        int ans = 0;
        while (!queue.isEmpty()) {
            ++ans;
            int size = queue.size();
            for (int i = 0; i < size; ++i) {
                int[] cell = queue.poll();
                int row = cell[0], column = cell[1];
                for (int[] dir : dirs) {
                    int newRow = row + dir[0], newColumn = column + dir[1];
                    if (newRow >= 0 && newRow < rows && newColumn >= 0 && newColumn < columns && matrix[newRow][newColumn] < matrix[row][column]) {
                        --outdegrees[newRow][newColumn];
                        if (outdegrees[newRow][newColumn] == 0) {
                            queue.offer(new int[]{newRow, newColumn});
                        }
                    }
                }
            }
        }
        return ans;
    }
}

class Solution:

    DIRS = [(-1, 0), (1, 0), (0, -1), (0, 1)]

    def longestIncreasingPath(self, matrix: List[List[int]]) -> int:
        if not matrix:
            return 0
        
        rows, columns = len(matrix), len(matrix[0])
        outdegrees = [[0] * columns for _ in range(rows)]
        queue = collections.deque()
        for i in range(rows):
            for j in range(columns):
                for dx, dy in Solution.DIRS:
                    newRow, newColumn = i + dx, j + dy
                    if 0 <= newRow < rows and 0 <= newColumn < columns and matrix[newRow][newColumn] > matrix[i][j]:
                        outdegrees[i][j] += 1
                if outdegrees[i][j] == 0:
                    queue.append((i, j))

        ans = 0
        while queue:
            ans += 1
            size = len(queue)
            for _ in range(size):
                row, column = queue.popleft()
                for dx, dy in Solution.DIRS:
                    newRow, newColumn = row + dx, column + dy
                    if 0 <= newRow < rows and 0 <= newColumn < columns and matrix[newRow][newColumn] < matrix[row][column]:
                        outdegrees[newRow][newColumn] -= 1
                        if outdegrees[newRow][newColumn] == 0:
                            queue.append((newRow, newColumn))
        
        return ans

var (
    dirs = [][]int{[]int{-1, 0}, []int{1, 0}, []int{0, -1}, []int{0, 1}}
    rows, columns int
)

func longestIncreasingPath(matrix [][]int) int {
    if len(matrix) == 0 || len(matrix[0]) == 0 {
        return 0
    }
    rows, columns = len(matrix), len(matrix[0])
    outdegrees := make([][]int, rows)
    for i := 0; i < rows; i++ {
        outdegrees[i] = make([]int, columns)
    }
    for i := 0; i < rows; i++ {
        for j := 0; j < columns; j++ {
            for _, dir := range dirs {
                newRow, newColumn := i + dir[0], j + dir[1]
                if newRow >= 0 && newRow < rows && newColumn >= 0 && newColumn < columns && matrix[newRow][newColumn] > matrix[i][j] {
                    outdegrees[i][j]++
                }
            }
        }
    }

    queue := [][]int{}
    for i := 0; i < rows; i++ {
        for j := 0; j < columns; j++ {
            if outdegrees[i][j] == 0 {
                queue = append(queue, []int{i, j})
            }
        }
    }
    ans := 0
    for len(queue) != 0 {
        ans++
        size := len(queue)
        for i := 0; i < size; i++ {
            cell := queue[0]
            queue = queue[1:]
            row, column := cell[0], cell[1]
            for _, dir := range dirs {
                newRow, newColumn := row + dir[0], column + dir[1]
                if newRow >= 0 && newRow < rows && newColumn >= 0 && newColumn < columns && matrix[newRow][newColumn] < matrix[row][column] {
                    outdegrees[newRow][newColumn]--
                    if outdegrees[newRow][newColumn] == 0 {
                        queue = append(queue, []int{newRow, newColumn})
                    }
                }
            }
        }
    }
    return ans
}

第三百三十题：

class Solution {
public:
    int minPatches(vector<int>& nums, int n) {
        long long x = 1;
        int i = 0, res = 0;
        while (x <= n) {
            if (i < nums.size() && nums[i] <= x) x += nums[i ++ ];
            else {
                x += x;
                res ++ ;
            }
        }
        return res;
    }
};

class Solution {
    public int minPatches(int[] nums, int n) {
        int patches = 0;
        long x = 1;
        int length = nums.length, index = 0;
        while (x <= n) {
            if (index < length && nums[index] <= x) {
                x += nums[index];
                index++;
            } else {
                x *= 2;
                patches++;
            }
        }
        return patches;
    }
}

class Solution:
    def minPatches(self, nums: List[int], n: int) -> int:
        patches, x = 0, 1
        length, index = len(nums), 0

        while x <= n:
            if index < length and nums[index] <= x:
                x += nums[index]
                index += 1
            else:
                x <<= 1
                patches += 1
        
        return patches

func minPatches(nums []int, n int) (patches int) {
    for i, x := 0, 1; x <= n; {
        if i < len(nums) && nums[i] <= x {
            x += nums[i]
            i++
        } else {
            x *= 2
            patches++
        }
    }
    return
}

第三百三十一题：

class Solution {
public:
    int k;
    string s;
    bool isValidSerialization(string _s) {
        k = 0;
        s = _s + ',';
        if (!dfs()) return false;
        return k == s.size();
    }
    bool dfs() {
        if (k == s.size()) return false;
        if (s[k] == '#') return k += 2, true;
        while (s[k] != ',') k ++ ;
        k ++ ;
        return dfs() && dfs();
    }
};

class Solution {
  public boolean isValidSerialization(String preorder) {
    // number of available slots
    int slots = 1;

    int n = preorder.length();
    for(int i = 0; i < n; ++i) {
      if (preorder.charAt(i) == ',') {
        // one node takes one slot
        --slots;

        // no more slots available
        if (slots < 0) return false;

        // non-empty node creates two children slots
        if (preorder.charAt(i - 1) != '#') slots += 2;
      }
    }

    // the last node
    slots = (preorder.charAt(n - 1) == '#') ? slots - 1 : slots + 1;
    // all slots should be used up
    return slots == 0;
  }
}

class Solution:
    def isValidSerialization(self, preorder: str) -> bool:
        num=1
        preorder=preorder.split(',')
        for i in preorder:
            if num==0:return False
            if i =='#':
                num-=1
                if num<0:return False
            else:
                num+=1
        if num==0:return True
        else:return False

func isValidSerialization(preorder string) bool {
	// 每个非空节点都有两个出度,每个结点都有一个入度(根节点除外), 出度==入度+1
	splits := strings.Split(preorder, ",")
	edge := 1
	for _, str := range splits {
		edge--
        if edge < 0 {
			break
		}
		if str != "#" {
			edge += 2
		}
	}
	return edge == 0
}

第三百三十二题：

class Solution {
public:
    unordered_map<string, multiset<string>> g;
    vector<string> ans;
    vector<string> findItinerary(vector<vector<string>>& tickets) {
        for (auto& e: tickets) g[e[0]].insert(e[1]);
        dfs("JFK");
        reverse(ans.begin(), ans.end());
        return ans;
    }
    void dfs(string u) {
        while (g[u].size()) {
            auto ver = *g[u].begin();
            g[u].erase(g[u].begin());
            dfs(ver);
        }
        ans.push_back(u);
    }
};

class Solution {
    Map<String, PriorityQueue<String>> map = new HashMap<String, PriorityQueue<String>>();
    List<String> itinerary = new LinkedList<String>();

    public List<String> findItinerary(List<List<String>> tickets) {
        for (List<String> ticket : tickets) {
            String src = ticket.get(0), dst = ticket.get(1);
            if (!map.containsKey(src)) {
                map.put(src, new PriorityQueue<String>());
            }
            map.get(src).offer(dst);
        }
        dfs("JFK");
        Collections.reverse(itinerary);
        return itinerary;
    }

    public void dfs(String curr) {
        while (map.containsKey(curr) && map.get(curr).size() > 0) {
            String tmp = map.get(curr).poll();
            dfs(tmp);
        }
        itinerary.add(curr);
    }
}

class Solution:
    def findItinerary(self, tickets: List[List[str]]) -> List[str]:
        def dfs(curr: str):
            while vec[curr]:
                tmp = heapq.heappop(vec[curr])
                dfs(tmp)
            stack.append(curr)

        vec = collections.defaultdict(list)
        for depart, arrive in tickets:
            vec[depart].append(arrive)
        for key in vec:
            heapq.heapify(vec[key])
        
        stack = list()
        dfs("JFK")
        return stack[::-1]

func findItinerary(tickets [][]string) []string {
    var (
        m  = map[string][]string{}
        res []string
    )
    
    for _, ticket := range tickets {
        src, dst := ticket[0], ticket[1]
        m[src] = append(m[src], dst)
    }
    for key := range m {
        sort.Strings(m[key])
    }

    var dfs func(curr string)
    dfs = func(curr string) {
        for {
            if v, ok := m[curr]; !ok || len(v) == 0 {
                break
            }
            tmp := m[curr][0]
            m[curr] = m[curr][1:]
            dfs(tmp)
        }
        res = append(res, curr)
    }

    dfs("JFK")
    for i := 0; i < len(res)/2; i++ {
        res[i], res[len(res) - 1 - i] = res[len(res) - 1 - i], res[i]
    }
    return res
}

第三百三十四题：

class Solution {
public:
    bool increasingTriplet(vector<int>& nums) {
        vector<int> q(2, INT_MAX);
        for (auto a: nums) {
            int k = 2;
            while (k > 0 && q[k - 1] >= a) k -- ;
            if (k == 2) return true;
            q[k] = a;
        }
        return false;
    }
};

class Solution {
    public boolean increasingTriplet(int[] nums) {
        int one = Integer.MAX_VALUE,two = Integer.MAX_VALUE;
        for(int three : nums){
            if(three > two) return true;
            else if(three <= one) one = three;
            else two = three;
            // if(three > one && three < two) two = three;
        }
        return false;
    }
}

class Solution:
    def increasingTriplet(self, nums: List[int]) -> bool:
        r1, r2 = sys.maxsize, sys.maxsize
        for n in nums :
            if n <= r1 : r1 = n
            elif n <= r2 : r2 = n
            else : return True
        return False

func increasingTriplet(nums []int) bool {
    m1, m2 := math.MaxInt64, math.MaxInt64

	for i := 0; i < len(nums); i++ {
		if m1 >= nums[i] {
			m1 = nums[i]
		} else if m2 >= nums[i] {
			m2 = nums[i]
		} else {
			return true
		}
	}

	return false
}

第三百三十五题：

class Solution {
public:
    bool isSelfCrossing(vector<int>& x) {
        int n = x.size();
        if (n <= 3) return false;
        for (int i = 3; i < n; i ++ ) {
            if (x[i - 1] <= x[i - 3] && x[i] >= x[i - 2]) return true;
            if (i >= 4 && x[i - 3] == x[i - 1] && x[i] + x[i - 4] >= x[i - 2]) return true;
            if (i >= 5 && x[i - 3] >= x[i - 1] && x[i - 1] + x[i - 5] >= x[i - 3] && x[i - 2] >= x[i - 4] && x[i - 4] + x[i] >= x[i - 2])
                return true;
        }
        return false;
    }
};

class Solution {
    public boolean isSelfCrossing(int[] x) {
        if(x.length <= 3)
            return false;
        int i, xl = x[1], yl = x[0], px = 0, py = 0;
        //检测a类型路径的变化趋势
        for(i = 2; i < x.length; i++){
            if((i & 0x1) == 1){
                if(x[i] <= xl){
                    //a ---> b
                    if(xl - px <= x[i])
                        yl -= py;
                    xl = x[i];
                    break;
                }
                //用px保存xl的旧值
                px = xl;
                xl = x[i];
            }else {
                if(x[i] <= yl){
                    //a ---> b
                    if(yl - py <= x[i])
                        xl -= px;
                    yl = x[i];
                    break;
                }
                //用py保存yl的旧值
                py = yl;
                yl = x[i];
            }
        }
        //检测b类型路径的变化趋势
        for(i++; i < x.length; i++){
            if((i & 0x1) == 1 && x[i] < xl){
                xl = x[i];
            }else if(x[i] < yl){
                yl = x[i];
            }else{
                return true;
            }
        }
        return false;
    }
}

class Solution:
    def isSelfCrossing(self, x) -> bool:
        if len(x) <  4:return False
        if len(x) == 4:return True if x[3] >= x[1] and x[2] <= x[0] else False
        for i in range(3, len(x)):
            if x[i] >= x[i-2] and x[i-1] <= x[i-3]:
                return True
            if i > 3 and x[i-1] == x[i-3] and x[i-4] + x[i] >= x[i-2]:
                return True
            if i > 4 and x[i-3]-x[i-5] <= x[i-1] <= x[i-3] and x[i-2]-x[i-4] <= x[i] <= x[i-2] and x[i-2] > x[i-4]:
                return True
        return False

第三百三十六题：

class Solution {
public:
    bool check(string& s) {
        for (int i = 0, j = s.size() - 1; i < j; i ++, j -- )
            if (s[i] != s[j])
                return false;
        return true;
    }
    vector<vector<int>> palindromePairs(vector<string>& words) {
        unordered_map<string, int> hash;
        for (int i = 0; i < words.size(); i ++ ) {
            auto w = words[i];
            reverse(w.begin(), w.end());
            hash[w] = i;
        }
        vector<vector<int>> res;
        for (int i = 0; i < words.size(); i ++ ) {
            auto w = words[i];
            for (int j = 0; j <= w.size(); j ++ ) {
                auto left = w.substr(0, j), right = w.substr(j);
                if (check(right) && hash.count(left) && hash[left] != i) res.push_back({i, hash[left]});
                if (check(left) && hash.count(right) && hash[right] != i && w.size() != words[hash[right]].size())
                    res.push_back({hash[right], i});
            }
        }
        return res;
    }
};

class Solution {
    List<String> wordsRev = new ArrayList<String>();
    Map<String, Integer> indices = new HashMap<String, Integer>();

    public List<List<Integer>> palindromePairs(String[] words) {
        int n = words.length;
        for (String word: words) {
            wordsRev.add(new StringBuffer(word).reverse().toString());
        }
        for (int i = 0; i < n; ++i) {
            indices.put(wordsRev.get(i), i);
        }

        List<List<Integer>> ret = new ArrayList<List<Integer>>();
        for (int i = 0; i < n; i++) {
            String word = words[i];
            int m = words[i].length();
            if (m == 0) {
                continue;
            }
            for (int j = 0; j <= m; j++) {
                if (isPalindrome(word, j, m - 1)) {
                    int leftId = findWord(word, 0, j - 1);
                    if (leftId != -1 && leftId != i) {
                        ret.add(Arrays.asList(i, leftId));
                    }
                }
                if (j != 0 && isPalindrome(word, 0, j - 1)) {
                    int rightId = findWord(word, j, m - 1);
                    if (rightId != -1 && rightId != i) {
                        ret.add(Arrays.asList(rightId, i));
                    }
                }
            }
        }
        return ret;
    }

    public boolean isPalindrome(String s, int left, int right) {
        int len = right - left + 1;
        for (int i = 0; i < len / 2; i++) {
            if (s.charAt(left + i) != s.charAt(right - i)) {
                return false;
            }
        }
        return true;
    }

    public int findWord(String s, int left, int right) {
        return indices.getOrDefault(s.substring(left, right + 1), -1);
    }
}

class Solution:
    def palindromePairs(self, words: List[str]) -> List[List[int]]:

        def findWord(s: str, left: int, right: int) -> int:
            return indices.get(s[left:right+1], -1)
        
        def isPalindrome(s: str, left: int, right: int) -> bool:
            return (sub := s[left:right+1]) == sub[::-1]
        
        n = len(words)
        indices = {word[::-1]: i for i, word in enumerate(words)}
        
        ret = list()
        for i, word in enumerate(words):
            m = len(word)
            for j in range(m + 1):
                if isPalindrome(word, j, m - 1):
                    leftId = findWord(word, 0, j - 1)
                    if leftId != -1 and leftId != i:
                        ret.append([i, leftId])
                if j and isPalindrome(word, 0, j - 1):
                    rightId = findWord(word, j, m - 1)
                    if rightId != -1 and rightId != i:
                        ret.append([rightId, i])

        return ret

func palindromePairs(words []string) [][]int {
    wordsRev := []string{}
    indices := map[string]int{}

    n := len(words)
    for _, word := range words {
        wordsRev = append(wordsRev, reverse(word))
    }
    for i := 0; i < n; i++ {
        indices[wordsRev[i]] = i
    }

    ret := [][]int{}
    for i := 0; i < n; i++ {
        word := words[i]
        m := len(word)
        if m == 0 {
            continue
        }
        for j := 0; j <= m; j++ {
            if isPalindrome(word, j, m - 1) {
                leftId := findWord(word, 0, j - 1, indices)
                if leftId != -1 && leftId != i {
                    ret = append(ret, []int{i, leftId})
                }
            }
            if j != 0 && isPalindrome(word, 0, j - 1) {
                rightId := findWord(word, j, m - 1, indices)
                if rightId != -1 && rightId != i {
                    ret = append(ret, []int{rightId, i})
                }
            }
        }
    }
    return ret
}

func findWord(s string, left, right int, indices map[string]int) int {
    if v, ok := indices[s[left:right+1]]; ok {
        return v
    }
    return -1
}

func isPalindrome(s string, left, right int) bool {
    for i := 0; i < (right - left + 1) / 2; i++ {
        if s[left + i] != s[right - i] {
            return false
        }
    }
    return true
}

func reverse(s string) string {
    n := len(s)
    b := []byte(s)
    for i := 0; i < n/2; i++ {
        b[i], b[n-i-1] = b[n-i-1], b[i]
    }
    return string(b)
}

标签：return,matrix,int,336,len,++,&&,329,LeetCode
来源： https://blog.csdn.net/weixin_44169596/article/details/113841338