u

top-100-liked/12_test.go

@@ -0,0 +1,59 @@
+package top100liked
+
+import "testing"
+
+// https://leetcode.cn/problems/minimum-window-substring/?envType=study-plan-v2&envId=top-100-liked
+
+func minWindow(s string, t string) string {
+	if len(t) > len(s) {
+		return ""
+	}
+	need := make(map[byte]int)
+	for _, v := range []byte(t) {
+		need[v]++
+	}
+
+	window := make(map[byte]int)
+	valid := 0
+	left := 0
+	minLen := len(s) + 1
+	start := 0
+
+	for right := 0; right < len(s); right++ {
+		ch := s[right]
+		if _, ok := need[ch]; ok {
+			window[ch]++
+			if window[ch] == need[ch] {
+				valid++
+			}
+		}
+
+		for valid == len(need) {
+			if right-left+1 < minLen {
+				minLen = right - left + 1
+				start = left
+			}
+
+			d := s[left]
+			left++
+			if _, ok := need[d]; ok {
+				if window[d] == need[d] {
+					valid--
+				}
+				window[d]--
+			}
+		}
+	}
+
+	if minLen == len(s)+1 {
+		return ""
+	}
+
+	return s[start : start+minLen]
+}
+
+func TestS12(t *testing.T) {
+	println(minWindow("ADOBECODEBANC", "ABC"))
+	println(minWindow("a", "a"))
+	println(minWindow("a", "aa"))
+}

top-100-liked/13_1_test.go

@@ -0,0 +1,47 @@
+package top100liked
+
+import "testing"
+
+// https://leetcode.cn/problems/best-time-to-buy-and-sell-stock/
+
+// 贪心
+func maxProfit(prices []int) int {
+	minPrice := prices[0] // 历史最低买入价
+	maxProfit := 0
+
+	for i := 1; i < len(prices); i++ {
+		// 如果今天卖，能赚多少？
+		profit := prices[i] - minPrice
+		maxProfit = max(maxProfit, profit)
+
+		// 更新历史最低价
+		minPrice = min(minPrice, prices[i])
+	}
+	return maxProfit
+}
+
+// 动态规划
+// dp[n][0] 第 n 天手中不持有股票时的最大利润
+// dp[n][1] 第 n 天手中持有股票时的最大利润
+// func maxProfit(prices []int) int {
+// 	n := len(prices)
+// 	if n == 0 {
+// 		return 0
+// 	}
+
+// 	dp := make([][2]int, n)
+// 	dp[0][0] = 0
+// 	dp[0][1] = -prices[0]
+
+// 	for i := 1; i < n; i++ {
+// 		dp[i][0] = max(dp[i-1][0], dp[i-1][1]+prices[i])
+// 		dp[i][1] = max(dp[i-1][1], -prices[i])
+// 	}
+
+// 	return dp[n-1][0]
+// }
+
+func TestS13_1(t *testing.T) {
+	println(maxProfit([]int{7, 1, 5, 3, 6, 4}))
+	println(maxProfit([]int{7, 6, 4, 3, 1}))
+}

top-100-liked/13_test.go

@@ -0,0 +1,43 @@
+package top100liked
+
+import "testing"
+
+// 爆内存
+// func maxSubArray(nums []int) int {
+// 	l := len(nums)
+// 	msa := make([][]int, l)
+// 	for i := range msa {
+// 		msa[i] = make([]int, l)
+// 	}
+// 	res := nums[0]
+// 	for i, v := range nums {
+// 		msa[i][i] = v
+// 		res = max(res, v)
+// 	}
+// 	for i := range l {
+// 		for j := i + 1; j < l; j++ {
+// 			msa[i][j] = msa[i][j-1] + nums[j]
+// 			res = max(res, msa[i][j])
+// 		}
+// 	}
+// 	return res
+// }
+
+func maxSubArray(nums []int) int {
+	dp := make([]int, len(nums))
+	dp[0] = nums[0]
+	maxSoFar := nums[0]
+
+	for i := 1; i < len(nums); i++ {
+		dp[i] = max(nums[i], dp[i-1]+nums[i])
+		maxSoFar = max(maxSoFar, dp[i])
+	}
+	return maxSoFar
+}
+
+func TestS13(t *testing.T) {
+	println(maxSubArray([]int{-2, 1, -3, 4, -1, 2, 1, -5, 4}))
+	println(maxSubArray([]int{1}))
+	println(maxSubArray([]int{5, 4, -1, 7, 8}))
+	println(maxSubArray([]int{-2, 1}))
+}

top-100-liked/14_test.go

@@ -0,0 +1,40 @@
+package top100liked
+
+import (
+	"cmp"
+	"fmt"
+	"slices"
+	"testing"
+)
+
+// https://leetcode.cn/problems/merge-intervals/?envType=study-plan-v2&envId=top-100-liked
+
+func merge(intervals [][]int) [][]int {
+	if len(intervals) <= 1 {
+		return intervals
+	}
+
+	slices.SortFunc(intervals, func(a, b []int) int {
+		return cmp.Compare(a[0], b[0])
+	})
+	res := [][]int{}
+	cur := intervals[0]
+	for i := 1; i < len(intervals); i++ {
+		new := intervals[i]
+		// 判断是否重叠
+		if cur[0] <= new[0] && new[0] <= cur[1] {
+			cur = []int{cur[0], max(cur[1], new[1])}
+		} else {
+			res = append(res, cur)
+			cur = new
+		}
+	}
+	res = append(res, cur)
+	return res
+}
+
+func TestS14(t *testing.T) {
+	fmt.Printf("%+v\n", merge([][]int{{1, 3}, {2, 6}, {8, 10}, {15, 18}}))
+	fmt.Printf("%+v\n", merge([][]int{{1, 4}, {4, 5}}))
+	fmt.Printf("%+v\n", merge([][]int{{4, 7}, {1, 4}}))
+}

top-100-liked/15_test.go

@@ -0,0 +1,58 @@
+package top100liked
+
+import (
+	"fmt"
+	"slices"
+	"testing"
+)
+
+// https://leetcode.cn/problems/rotate-array/description/?envType=study-plan-v2&envId=top-100-liked
+
+func rotate(nums []int, k int) {
+	if k == 0 {
+		return
+	}
+	n := len(nums)
+	slices.Reverse(nums)
+	slices.Reverse(nums[:k%n])
+	slices.Reverse(nums[k%n:])
+}
+
+// func rotate(nums []int, k int) {
+// 	n := len(nums)
+// 	k = k % n
+// 	if k == 0 {
+// 		return
+// 	}
+
+// 	count := 0 // 已经处理了多少个元素
+// 	for start := 0; count < n; start++ {
+// 		current := start
+// 		prev := nums[start] // 暂存起点元素
+
+// 		// 沿着环跳动
+// 		for {
+// 			next := (current + k) % n
+// 			// 把 prev 放到 next 位置，同时保存 next 原来的值作为新的 prev
+// 			nums[next], prev = prev, nums[next]
+// 			current = next
+// 			count++
+
+// 			if current == start {
+// 				break // 回到起点，这条环走完了
+// 			}
+// 		}
+// 	}
+// }
+
+func TestS15(t *testing.T) {
+	input := []int{1, 2, 3, 4, 5, 6, 7}
+	rotate(input, 3)
+	fmt.Printf("%+v\n", input)
+	input = []int{-1, -100, 3, 99}
+	rotate(input, 2)
+	fmt.Printf("%+v\n", input)
+	input = []int{-1}
+	rotate(input, 2)
+	fmt.Printf("%+v\n", input)
+}

top-100-liked/16_test.go

@@ -0,0 +1,57 @@
+package top100liked
+
+import (
+	"fmt"
+	"testing"
+)
+
+// https://leetcode.cn/problems/product-of-array-except-self/?envType=study-plan-v2&envId=top-100-liked
+
+// func productExceptSelf(nums []int) []int {
+// 	left := make([]int, len(nums))
+// 	right := make([]int, len(nums))
+// 	left[0] = nums[0]
+// 	right[len(nums)-1] = nums[len(nums)-1]
+// 	for i := 1; i < len(nums); i++ {
+// 		left[i] = left[i-1] * nums[i]
+// 	}
+// 	for i := len(nums) - 2; i >= 0; i-- {
+// 		right[i] = right[i+1] * nums[i]
+// 	}
+// 	res := []int{}
+// 	for i := range nums {
+// 		if i == 0 {
+// 			res = append(res, right[1])
+// 		} else if i == len(nums)-1 {
+// 			res = append(res, left[len(nums)-2])
+// 		} else {
+// 			res = append(res, left[i-1]*right[i+1])
+// 		}
+// 	}
+// 	return res
+// }
+
+func productExceptSelf(nums []int) []int {
+	n := len(nums)
+	answer := make([]int, n)
+
+	// 第一遍：计算左边乘积，存入 answer
+	answer[0] = 1
+	for i := 1; i < n; i++ {
+		answer[i] = answer[i-1] * nums[i-1]
+	}
+
+	// 第二遍：从右向左，用 R 维护右边乘积
+	R := 1
+	for i := n - 1; i >= 0; i-- {
+		answer[i] = answer[i] * R // 左边积 × 右边积
+		R = R * nums[i]           // 更新右边积
+	}
+
+	return answer
+}
+
+func TestS16(t *testing.T) {
+	fmt.Printf("%+v", productExceptSelf([]int{1, 2, 3, 4}))
+	fmt.Printf("%+v", productExceptSelf([]int{-1, 1, 0, -3, 3}))
+}

top-100-liked/17_test.go

@@ -0,0 +1,31 @@
+package top100liked
+
+import "testing"
+
+// https://leetcode.cn/problems/first-missing-positive/description/?envType=study-plan-v2&envId=top-100-liked
+
+func firstMissingPositive(nums []int) int {
+	n := len(nums)
+	for i := range nums {
+		for nums[i] >= 1 && nums[i] <= n && nums[i] != i+1 {
+			if nums[i] != nums[nums[i]-1] { // 关键条件，否则会死循环 [1, 1]
+				nums[i], nums[nums[i]-1] = nums[nums[i]-1], nums[i]
+			} else {
+				break
+			}
+		}
+	}
+	for i, v := range nums {
+		if v != i+1 {
+			return i + 1
+		}
+	}
+	return n + 1
+}
+
+func TestS17(t *testing.T) {
+	// println(firstMissingPositive([]int{1, 2, 0}))
+	// println(firstMissingPositive([]int{3, 4, -1, 1}))
+	// println(firstMissingPositive([]int{7, 8, 9, 11, 12}))
+	println(firstMissingPositive([]int{1, 1}))
+}