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

Example:

Input: [2,1,5,6,2,3]
Output: 10

方法1:

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

時間複雜度：O(n)

空間複雜度：O(n)

https://github.com/zhangyu345293721/leetcode