u

top-100-liked/73/leetcode_test.go

@@ -1,48 +1,60 @@
 package top100liked
 
 import (
-	"math/rand"
+	"fmt"
 	"testing"
 )
 
-// https://leetcode.cn/problems/kth-largest-element-in-an-array/?envType=study-plan-v2&envId=top-100-liked
+// https://leetcode.cn/problems/largest-rectangle-in-histogram/?envType=study-plan-v2&envId=top-100-liked
 
-func findKthLargest(nums []int, k int) int {
-	n := len(nums)
-	target := n - k // 第 k 大 = 升序第 n-k 位
-	var quickSelect func(l, r int) int
-	quickSelect = func(l, r int) int {
-		if l == r {
-			return nums[l]
+// 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
 		}
-		pivot := nums[l+rand.Intn(r-l+1)]
-		// 三路分区：[l..lt-1] < pivot, [lt..gt] == pivot, [gt+1..r] > pivot
-		lt, gt, i := l, r, l
-		for i <= gt {
-			switch {
-			case nums[i] < pivot:
-				nums[lt], nums[i] = nums[i], nums[lt]
-				lt++
-				i++
-			case nums[i] > pivot:
-				nums[gt], nums[i] = nums[i], nums[gt]
-				gt--
-			default:
-				i++
+		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)
 			}
-		}
-		switch {
-		case target < lt:
-			return quickSelect(l, lt-1)
-		case target > gt:
-			return quickSelect(gt+1, r)
-		default:
-			return pivot
+			stack = append(stack, i)
 		}
 	}
-	return quickSelect(0, n-1)
+	return maxArea
 }
 
 func Test(t *testing.T) {
-	findKthLargest([]int{3, 2, 1, 5, 6, 4}, 2)
+	fmt.Println(largestRectangleArea([]int{2, 1, 5, 6, 2, 3}))
+	fmt.Println(largestRectangleArea([]int{1}))
+	fmt.Println(largestRectangleArea([]int{2, 1, 2}))
 }