题目

类型：Stack

难度：困难

解题思路

https://leetcode-cn.com/problems/largest-rectangle-in-histogram/solution/zhu-zhuang-tu-zhong-zui-da-de-ju-xing-by-leetcode-/
看题解中的PPT有助于理解

代码

class Solution {
    public int largestRectangleArea(int[] heights) {
        int n = heights.length;
        int[] left = new int[n];
        int[] right = new int[n];
        Arrays.fill(right, n);
        Stack<Integer> mono_stack = new Stack<Integer>();
        for (int i = 0; i < n; ++i) {
            while (!mono_stack.isEmpty() && heights[mono_stack.peek()] >= heights[i]) {
                right[mono_stack.peek()] = i;
                mono_stack.pop();
            }
            left[i] = (mono_stack.isEmpty() ? -1 : mono_stack.peek());
            mono_stack.push(i);
        }
        int ans = 0;
        for (int i = 0; i < n; ++i) {
            ans = Math.max(ans, (right[i] - left[i] - 1) * heights[i]);
        }
        return ans;
    }
}