P2895 [USACO08FEB]Meteor Shower S

// Problem: P2895 [USACO08FEB]Meteor Shower S
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P2895
// Memory Limit: 125 MB
// Time Limit: 1000 ms
// User: Pannnn

#include <bits/stdc++.h>

using namespace std;

template<class T>
void debugVector(const T &a) {
    cout << "[ ";
    for (size_t i = 0; i < a.size(); ++i) {
        cout << a[i] << (i == a.size() - 1 ? " " : ", ");
    }
    cout << "]" << endl;
}

template<class T1, class T2>
void debugVectorPair(const vector<pair<T1, T2>> &a) {
    cout << "{";
    for (size_t i = 0; i < a.size(); ++i) {
        cout << "[ " << a[i].first << ": " << a[i].second << (i == a.size() - 1 ? " ]" : " ], ");
    }
    cout << "}" << endl;
}


template<class T>
void debugMatrix2(const T &a) {
    for (size_t i = 0; i < a.size(); ++i) {
        debugVector(a[i]);
    }
}

template<class T>
using matrix2 = vector<vector<T>>;

template<class T>
vector<vector<T>> getMatrix2(size_t n, size_t m, T init = T()) {
    return vector<vector<T>>(n, vector<T>(m, init));
}

template<class T>
using matrix3 = vector<vector<vector<T>>>;

template<class T>
vector<vector<vector<T>>> getMatrix3(size_t x, size_t y, size_t z, T init = T()) {
    return vector<vector<vector<T>>>(x, vector<vector<T>>(y, vector<T>(z, init)));
}

vector<int> genBigInteger(const string &a) {
    vector<int> res;
    if (a.empty()) return res;
    for (int i = a.size() - 1; i >= 0; --i) {
        res.push_back(a[i] - '0');
    }
    return res;
}

ostream &printBigInteger(const vector<int> &a) {
    if (a.empty()) return cout;
    for (int i = a.size() - 1; i >= 0; --i) {
        cout << a[i];
    }
    return cout;
}

vector<int> maxBigInteger(const vector<int> &a, const vector<int> &b) {
    if (a.size() > b.size()) {
        return a;
    } else if (a.size() < b.size()) {
        return b;
    }
    for (int i = a.size() - 1; i >= 0; --i) {
        if (a[i] > b[i]) {
            return a;
        } else if (a[i] < b[i]) {
            return b;
        }
    }
    return a;
}

vector<int> addBigInteger(const vector<int> &a, const vector<int> &b) {
    vector<int> res;
    int pre = 0;
    for (size_t i = 0; i < a.size() || i < b.size() || pre; ++i) {
        if (i < a.size()) pre += a[i];
        if (i < b.size()) pre += b[i];
        res.push_back(pre % 10);
        pre /= 10;
    }
    while (res.size() > 1 && res.back() == 0) {
        res.pop_back();
    }
    return res;
}

vector<int> mulBigInteger(const vector<int> &a, int b) {
    vector<int> res;
    int pre = 0;
    for (size_t i = 0; i < a.size() || pre; ++i) {
        if (i < a.size()) pre += a[i] * b;
        res.push_back(pre % 10);
        pre /= 10;
    }
    while (res.size() > 1 && res.back() == 0) {
        res.pop_back();
    }
    return res;
}

vector<int> divBigInteger(const vector<int> &a, int b, int &r) {
    vector<int> res;
    for (int i = a.size() - 1; i >= 0; --i) {
        r = 10 * r + a[i];
        res.push_back(r / b);
        r %= b;
    }
    reverse(res.begin(), res.end());
    while (res.size() > 1 && res.back() == 0) {
        res.pop_back();
    }
    return res;
}

int bfs(matrix2<int> &info) {
    if (info[0][0] == 0) {
        return -1;
    }
    info[0][0] = 0;
    vector<int> dx = {-1, 0, 1, 0};
    vector<int> dy = {0, 1, 0, -1};
    queue<pair<int, int>> q;
    q.push({0, 0});
    while (!q.empty()) {
        int tx = q.front().first;
        int ty = q.front().second;
        
        // 如果 范围在合法区间内 且 能够到达的时间小于变成焦土的时间 且 在此前没有到达过 更新到达此点的最短时间
        for (int i = 0; i < dx.size(); ++i) {
            if (tx + dx[i] > 310 || tx + dx[i] < 0 || ty + dy[i] > 310 || ty + dy[i] < 0 ||
                info[tx + dx[i]][ty + dy[i]] == 0 ||
                info[tx + dx[i]][ty + dy[i]] < 0 && info[tx][ty] + 1 >= -info[tx + dx[i]][ty + dy[i]] ||
                info[tx + dx[i]][ty + dy[i]] > 0 && info[tx][ty] + 1 >= info[tx + dx[i]][ty + dy[i]]) {
                continue;
            } else {
                if (info[tx + dx[i]][ty + dy[i]] == INT_MAX) {
                    return info[tx][ty] + 1;
                }
                info[tx +dx[i]][ty + dy[i]] = info[tx][ty] + 1;
                q.push({tx + dx[i], ty + dy[i]});
            }
        }
        q.pop();
    }
    return -1;
}

// 坑点：move to a new, safer location
// 不能在原地不动，没有翻译
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    int m;
    cin >> m;
    
    vector<int> dx = {0, -1, 0, 1, 0};
    vector<int> dy = {0, 0, 1, 0, -1};
    matrix2<int> info = getMatrix2(311, 311, INT_MAX);
    // 区域最早在t时间变为焦土。其值存储为-t。当遇到一个INT_MAX的格子，安全的格子
    for (int i = 0; i < m; ++i) {
        int x, y, t;
        cin >> x >> y >> t;
        for (int j = 0; j < dx.size(); ++j) {
            if (x + dx[j] > 310 || x + dx[j] < 0 || y + dy[j] > 310 || y + dy[j] < 0 ||
                info[x + dx[j]][y + dy[j]] == 0 ||
                info[x + dx[j]][y + dy[j]] < 0 && info[x + dx[j]][y + dy[j]] > -t) {
                continue;
            } else {
                info[x + dx[j]][y + dy[j]] = -t;
            }
        }
    }
    cout << bfs(info) << endl;    
    return 0;
}

标签：info,res,Shower,vector,dx,dy,USACO08FEB,P2895,size
来源： https://www.cnblogs.com/pannnn/p/16092100.html