LeetCode 热题 HOT 100 第二十天

Leetcode647. 回文子串

class Solution {
public:
    int countSubstrings(string s) {
        int n = s.size();
        int res = s.size();
        for (int i = 0; i < s.size(); i ++ ) {
            int l = i - 1, r = i + 1;
            while (l >= 0 && r < n && s[l] == s[r]) l --, r ++ , res ++ ;
            l = i, r = i + 1;
            while (l >= 0 && r < n && s[l] == s[r]) l --, r ++ , res ++ ;
        }
        return res;
    }
};

Leetcode739. 每日温度

思路：单调栈

class Solution {
public:
    vector<int> dailyTemperatures(vector<int>& T) {
        vector<int> res(T.size());
        stack<int> stk;
        for (int i = T.size() - 1; i >= 0; i -- ) {
            while (stk.size() && T[i] >= T[stk.top()]) stk.pop();
            if (stk.size()) {
                res[i] = stk.top() - i;
            }
            stk.push(i);
        }
        return res;
    }
};