Leetcode 398 随机数索引
作者:互联网
Given an integer array nums
with possible duplicates, randomly output the index of a given target
number. You can assume that the given target number must exist in the array.
Implement the Solution class:
Solution(int[] nums)
Initializes the object with the arraynums
.int pick(int target)
Picks a random indexi
fromnums
wherenums[i] == target
. If there are multiple valid i's, then each index should have an equal probability of returning.
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/random-pick-index
实现方法比较垃圾,差不多是离散化之后记录下每个数字出现的位置,然后记录有几个位置,然后循环输出(竟然真的会检测概率相等)。
class Solution {
public:
map<int, int> m;
vector<int> t, now;
vector<vector<int>> g;
Solution(vector<int>& nums) {
vector<int> cop = nums;
std::sort(nums.begin(), nums.end());
int N = nums.size(), cnt = 0;
m.insert(make_pair(nums[0], cnt++));
nums[0] = m[nums[0]], g.push_back(vector<int>()), t.push_back(0), now.push_back(0);
for (int i = 1; i < N; i++) {
if (nums[i] != nums[i-1]) m.insert(make_pair(nums[i], cnt++)), g.push_back(vector<int>()), t.push_back(0), now.push_back(0);
nums[i] = m[nums[i]];
}
for (int i = 0; i < N; i++) {
g[m[cop[i]]].push_back(i);
t[m[cop[i]]]++;
}
}
int pick(int target) {
if (m.find(target) == m.end()) return -1;
else {
int tem = m[target];
now[tem] = (now[tem] + 1) % t[tem];
return g[tem][now[tem]];
}
}
};
/**
* Your Solution object will be instantiated and called as such:
* Solution* obj = new Solution(nums);
* int param_1 = obj->pick(target);
*/
标签:target,nums,int,back,Solution,随机数,push,398,Leetcode 来源: https://www.cnblogs.com/Gensokyo-Alice/p/16192678.html