added leetcode 78 golang backtracking subsets

go/39-Combination-Sum.go

@@ -0,0 +1,24 @@
+package main
+
+func combinationSum(candidates []int, target int) [][]int {
+	ans := make([][]int, 0)
+	curr := make([]int, 0)
+	var backtrack func(idx int, currSum int, curr []int)
+	backtrack = func(idx int, currSum int, curr []int) {
+		if currSum == target {
+			ans = append(ans, append([]int{}, curr...))
+			return
+		}
+		if currSum > target {
+			return
+		}
+		for i := idx; i < len(candidates); i++ {
+			curr = append(curr, candidates[i])
+			backtrack(i, currSum+candidates[i], curr)
+			curr = curr[:len(curr)-1]
+		}
+
+	}
+	backtrack(0, 0, curr)
+	return ans
+}

go/40-Combination-Sum-II.go

@@ -0,0 +1,30 @@
+package main
+
+import "sort"
+
+func combinationSum2(candidates []int, target int) [][]int {
+	ans := make([][]int, 0)
+	curr := make([]int, 0)
+	sort.Ints(candidates)
+	var backtrack func(idx int, currSum int, curr []int)
+	backtrack = func(idx int, currSum int, curr []int) {
+		if currSum == target {
+			ans = append(ans, append([]int{}, curr...))
+			return
+		}
+		if currSum > target {
+			return
+		}
+		for i := idx; i < len(candidates); i++ {
+			if i > idx && candidates[i] == candidates[i-1] {
+				continue
+			}
+			curr = append(curr, candidates[i])
+			backtrack(i+1, currSum+candidates[i], curr)
+			curr = curr[:len(curr)-1]
+		}
+
+	}
+	backtrack(0, 0, curr)
+	return ans
+}

go/46-Permutations.go

@@ -0,0 +1,25 @@
+package main
+
+func permute(nums []int) [][]int {
+	n := len(nums)
+	ans := make([][]int, 0)
+	curr := make([]int, 0, n)
+	vis := make(map[int]int)
+	var backtrack func(idx int)
+	backtrack = func(idx int) {
+		if len(curr) == n {
+			ans = append(ans, append([]int{}, curr...))
+		}
+		for i := 0; i < n; i++ {
+			if vis[i] == 0 {
+				vis[i]++
+				curr = append(curr, nums[i])
+				backtrack(i + 1)
+				curr = curr[:len(curr)-1]
+				vis[i]--
+			}
+		}
+	}
+	backtrack(0)
+	return ans
+}

go/78-Subsets.go

@@ -0,0 +1,20 @@
+package main
+
+func subsets(nums []int) [][]int {
+	ans := make([][]int, 0)
+	curr := make([]int, 0)
+	var backtrack func(idx int)
+	backtrack = func(idx int) {
+		ans = append(ans, append([]int{}, curr...))
+		if idx == len(nums) {
+			return
+		}
+		for i := idx; i < len(nums); i++ {
+			curr = append(curr, nums[i])
+			backtrack(i + 1)
+			curr = curr[:len(curr)-1]
+		}
+	}
+	backtrack(0)
+	return ans
+}

go/90-Subsets-II.go

@@ -0,0 +1,25 @@
+package main
+
+import "sort"
+
+func subsetsWithDup(nums []int) [][]int {
+	n := len(nums)
+	ans := make([][]int, 0, 1<<n)
+	curr := make([]int, 0, n)
+	sort.Ints(nums)
+	var backtrack func(idx int)
+	backtrack = func(idx int) {
+		ans = append(ans, append([]int{}, curr...))
+		for i := idx; i < n; i++ {
+			if i > idx && nums[i] == nums[i-1] {
+				continue
+			}
+			curr = append(curr, nums[i])
+			//not backtrack(idx + 1)!!
+			backtrack(i + 1)
+			curr = curr[:len(curr)-1]
+		}
+	}
+	backtrack(0)
+	return ans
+}