LeetCode Largest Rectangle in Histogram （单调栈）

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.

题意：求直方图中最大面积的矩形。

思路：单调栈的应用。维持一个单调递增的栈，网上写的可以转来：题解

public class Solution {
    public int largestRectangleArea(int[] height) {
        Stack<Integer> stack = new Stack<Integer>();
        int i = 0;
        int ans = 0;
        int h[] = new int[height.length+1];
        h = Arrays.copyOf(height, height.length+1);
        while (i < h.length) {
        	if (stack.isEmpty() || h[stack.peek()] <= h[i])
        		stack.push(i++);
        	else {
        		int t = stack.pop();
        		ans = Math.max(ans, h[t] * (stack.isEmpty() ? i : i - stack.peek() - 1));
        	}
        }

        return ans;
    }
}