package top100liked

import (
	"fmt"
	"testing"
)

// https://leetcode.cn/problems/largest-rectangle-in-histogram/?envType=study-plan-v2&envId=top-100-liked

// 暴力法，超时
// func largestRectangleArea(heights []int) int {
// 	maxArea := 0
// 	// i 是每个组合中的元素数量
// 	for i := 1; i <= len(heights); i++ {
// 		// j 是在整个 heights 中滑动的次数
// 		for j := 0; j < len(heights)-i+1; j++ {
// 			// 计算
// 			maxArea = max(maxArea, slices.Min(heights[j:j+i])*i)
// 		}
// 	}
// 	return maxArea
// }

func largestRectangleArea(heights []int) int {
	stack := []int{}
	maxArea := 0
	for i := range len(heights) + 1 {
		if len(stack) == 0 {
			stack = append(stack, i)
			continue
		}
		var cur int
		if i == len(heights) {
			cur = 0
		} else {
			cur = heights[i]
		}
		if cur >= heights[stack[len(stack)-1]] {
			stack = append(stack, i)
		} else {
			for len(stack) > 0 && heights[stack[len(stack)-1]] > cur {
				top := stack[len(stack)-1]
				stack = stack[:len(stack)-1]
				width := i
				if len(stack) > 0 {
					width = i - stack[len(stack)-1] - 1
				}
				maxArea = max(maxArea, heights[top]*width)
			}
			stack = append(stack, i)
		}
	}
	return maxArea
}

func Test(t *testing.T) {
	fmt.Println(largestRectangleArea([]int{2, 1, 5, 6, 2, 3}))
	fmt.Println(largestRectangleArea([]int{1}))
	fmt.Println(largestRectangleArea([]int{2, 1, 2}))
}