84.直方图中最大矩阵

Largest Rectangle in Histogram

问题描述：

Given n non-negative integers representing the histogram’s bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.

Above is a histogram where width of each bar is 1, given height = [2,1,5,6,2,3].
The largest rectangle is shown in the shaded area, which has area = 10 unit.

参考答案：

class Solution {
public:
    int largestRectangleArea(vector<int>& heights) {
        stack<int> s;
        int i = 0;
        int maxarea = 0;

        while (i < heights.size()) {
            if (s.empty() || heights[i] >= heights[s.top()])
                s.push(i++);
            else {
                int h = heights[s.top()];
                s.pop();
                int w = s.empty() ? i : i-s.top()-1;

                maxarea = max(maxarea, h*w);
            }
        }

        while (!s.empty()) {
            int h = heights[s.top()];
            s.pop();
            int w = s.empty() ? i : i-s.top()-1;
            maxarea = max(maxarea, h*w);
        }

        return maxarea;
    }
};

性能：