leetcode: Largest Rectangle in Histogram

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.

For example,
Given height = [2,1,5,6,2,3],
return 10.

http://blog.csdn.net/doc_sgl/article/details/11805519

這篇分析寫得很好

class Solution {
public:
    int largestRectangleArea(vector<int> &height) {
        stack< int> stk;
        height.push_back(0);
        int res = 0;
        for( int i = 0; i < height.size(); ){
            if( stk.empty() || height[i] >= height[stk.top()]){
                stk.push(i++);
            }
            else{
                int tmp = stk.top();
                stk.pop();
                res = max( res, height[tmp] * ( stk.empty() ? i : i - stk.top() - 1));
            }
        }
        return res;
    }
};