leetcode五月每日一題 leetcode84

這道題如果用暴力解法的話，枚舉每一個矩形，然後來計算其面積。但是會報超時錯誤🙅

然後參考了一下；leetcode的官方題解

class Solution {
public:
    int largestRectangleArea(vector<int>& heights) {
        int n = heights.size();
        vector<int> left(n), right(n);
        
        stack<int> mono_stack;
        for (int i = 0; i < n; ++i) {
            while (!mono_stack.empty() && heights[mono_stack.top()] >= heights[i]) {
                mono_stack.pop();
            }
            left[i] = (mono_stack.empty() ? -1 : mono_stack.top());
            mono_stack.push(i);
        }

        mono_stack = stack<int>();
        for (int i = n - 1; i >= 0; --i) {
            while (!mono_stack.empty() && heights[mono_stack.top()] >= heights[i]) {
                mono_stack.pop();
            }
            right[i] = (mono_stack.empty() ? n : mono_stack.top());
            mono_stack.push(i);
        }
        
        int ans = 0;
        for (int i = 0; i < n; ++i) {
            ans = max(ans, (right[i] - left[i] - 1) * heights[i]);
        }
        return ans;
    }
};

五月爲啥還有31天，堅持一個月打卡真的好不容易啊。。。而且自己的論文還要二辯了。。。😭