84. Largest Rectangle in Histogram

最新推荐文章于 2022-01-15 14:46:52 发布

原创最新推荐文章于 2022-01-15 14:46:52 发布 · 352 阅读

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#LeetCode #Array #Stack #Largest Rectangle in

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本文介绍了一种使用单调栈求解直方图中最大矩形面积的问题。通过实例讲解了如何利用单调递增栈实现算法，包括关键步骤及代码实现。

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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 heights = [2,1,5,6,2,3],
return 10.

这道题考查单调栈的用法。这里的单调栈是单调递增栈，遇到比peek小的数，就开始弹栈，直到栈为空或者遇到比自己小的peek，并随时更新max。代码如下：

public class Solution {
    public int largestRectangleArea(int[] heights) {
        if (heights == null || heights.length == 0) {
            return 0;
        }
        Stack<Integer> stack = new Stack<Integer>();
        int max = 0;
        for (int i = 0; i <= heights.length; i ++) {
            int cur = i == heights.length? -1: heights[i];
            while (!stack.isEmpty() && cur <= heights[stack.peek()]) {
                int h = heights[stack.pop()];
                int w = stack.isEmpty()? i: i - stack.peek() - 1;
                max = Math.max(max, h * w);
            }
            stack.push(i);
        }
        return max;
    }
}