leetcode 84. 柱状图中最大的矩形

笨比master

于 2021-03-30 11:44:09 发布

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分类专栏： new leetcode 文章标签： leetcode 算法 stack

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84. 柱状图中最大的矩形

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class Solution {
public:
    int largestRectangleArea(vector<int>& heights) {
        stack<int> S;
        heights.push_back(0);
        S.push(-1);
        int max_area = 0;
        for(int ii = 0; ii < heights.size(); ii++) {
            while(S.top() != -1 && heights[ii] <= heights[S.top()]) {
                int height = heights[S.top()];
                S.pop();
                max_area = max(max_area, height * (ii - S.top() - 1));
            }
            S.push(ii);
        }
        return max_area;
    }
};

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class Solution {
public:
    int largestRectangleArea(vector<int>& heights) {
        int n = heights.size();
        int max_area = 0;
        vector<int> left(n, 0);
        vector<int> right(n, 0);
        for(int ii = 0; ii < n; ii++) {
            int jj = ii - 1;
            while(jj >= 0 && heights[jj] >= heights[ii]) jj = left[jj];
            left[ii] = jj;
        }
        for(int ii = n-1; ii >= 0; ii--) {
            int jj = ii + 1;
            while(jj < n && heights[jj] >= heights[ii]) jj = right[jj];
            right[ii] = jj;
            max_area = max(max_area, heights[ii] * (right[ii] - left[ii] - 1));
        }
        return max_area;
    }
};