第一周作业#29

Week_01/id_29/LeetCode_021_29.go

@@ -0,0 +1,39 @@
+package main
+
+// LeetCode - 021. Merge Two Sorted Lists
+// https://leetcode.com/problems/merge-two-sorted-lists/
+func mergeTwoLists(l1 *ListNode, l2 *ListNode) *ListNode {
+	// Check boundary condition
+	if l1 == nil {
+		return l2
+	}
+	if l2 == nil {
+		return l1
+	}
+
+	// Create dummy node
+	dummy := ListNode{}
+	head := &dummy
+
+	// Connect l1 and l2
+	for l1 != nil && l2 != nil {
+		if l1.Val < l2.Val {
+			head.Next = l1
+			l1 = l1.Next
+		} else {
+			head.Next = l2
+			l2 = l2.Next
+		}
+		head = head.Next
+	}
+
+	// Check leftover
+	if l1 != nil {
+		head.Next = l1
+	}
+	if l2 != nil {
+		head.Next = l2
+	}
+
+	return dummy.Next
+}

Week_01/id_29/LeetCode_024_29.go

@@ -0,0 +1,24 @@
+package main
+
+// LeetCode - 024. Swap Nodes in Pairs
+// https://leetcode.com/problems/swap-nodes-in-pairs/
+func swapPairs(head *ListNode) *ListNode {
+	dummy := ListNode{}
+	dummy.Next = head
+
+	pre := &dummy
+
+	for pre != nil {
+		if pre.Next == nil || pre.Next.Next == nil {
+			break
+		}
+
+		first := pre.Next
+		pre.Next = first.Next
+		first.Next = first.Next.Next
+		pre.Next.Next = first
+		pre = first
+	}
+
+	return dummy.Next
+}

Week_01/id_29/LeetCode_026_29.go

@@ -0,0 +1,16 @@
+package main
+
+// LeetCode - 026. Remove Duplicates from Sorted Array
+// https://leetcode.com/problems/remove-duplicates-from-sorted-array/
+func removeDuplicates(nums []int) int {
+	replaceIndex := 1
+
+	for curr := 1; curr < len(nums); curr++ {
+		if nums[curr] != nums[curr-1] {
+			nums[replaceIndex] = nums[curr]
+			replaceIndex++
+		}
+	}
+
+	return replaceIndex
+}

Week_01/id_29/LeetCode_049_29.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"sort"
+	"strings"
+)
+
+// LeetCode - 49. Group Anagrams
+// https://leetcode.com/problems/group-anagrams/
+func SortString(w string) string {
+	s := strings.Split(w, "")
+	sort.Strings(s)
+	return strings.Join(s, "")
+}
+
+func groupAnagrams(strs []string) [][]string {
+	m := make(map[string][]string)
+
+	for _, w := range strs {
+		word := SortString(w)
+		m[word] = append(m[word], w)
+	}
+
+	var ss [][]string
+	for e := range m {
+		ss = append(ss, m[e])
+	}
+	return ss
+}

Week_01/id_29/LeetCode_050_29.go

@@ -0,0 +1,21 @@
+package main
+
+// LeetCode - 50. Pow(x, n)
+// https://leetcode.com/problems/powx-n/
+func myPow(x float64, n int) float64 {
+	if n == 0 {
+		return 1
+	}
+	if n == 1 {
+		return x
+	}
+	if n < 0 {
+		return 1 / myPow(x, -n)
+	}
+
+	if n%2 == 0 {
+		return myPow(x*x, n/2)
+	} else {
+		return x * myPow(x*x, n/2)
+	}
+}

Week_01/id_29/LeetCode_088_29.go

@@ -0,0 +1,20 @@
+package main
+
+// LeetCode - 088. Merge Sorted Array
+// https://leetcode.com/problems/merge-sorted-array/
+func merge(nums1 []int, m int, nums2 []int, n int) {
+	replaceIndex := m + n - 1
+	array1Target := m - 1
+	array2Target := n - 1
+
+	for array2Target >= 0 {
+		if array1Target >= 0 && nums2[array2Target] < nums1[array1Target] {
+			nums1[replaceIndex] = nums1[array1Target]
+			array1Target--
+		} else {
+			nums1[replaceIndex] = nums2[array2Target]
+			array2Target--
+		}
+		replaceIndex--
+	}
+}

Week_01/id_29/LeetCode_104_29.go

@@ -0,0 +1,13 @@
+package main
+
+// LeetCode - 104. Maximum Depth of Binary Tree
+// https://leetcode.com/problems/maximum-depth-of-binary-tree/
+import "math"
+
+func maxDepth(root *TreeNode) int {
+	if root == nil {
+		return 0
+	}
+
+	return int(math.Max(float64(maxDepth(root.Left)), float64(maxDepth(root.Right))) + 1)
+}

Week_01/id_29/LeetCode_189_29.go

@@ -0,0 +1,21 @@
+package main
+
+// LeetCode - 189. Rotate Array
+// https://leetcode.com/problems/rotate-array/
+func rotate(nums []int, k int) {
+	n := len(nums)
+
+	k = k % n
+
+	reverse(nums, 0, n-1)
+	reverse(nums, 0, k-1)
+	reverse(nums, k, n-1)
+}
+
+func reverse(nums []int, i int, j int) {
+	for i < j {
+		nums[i], nums[j] = nums[j], nums[i]
+		i++
+		j--
+	}
+}

Week_01/id_29/LeetCode_242_29.go

@@ -0,0 +1,38 @@
+package main
+
+// LeetCode - 242. Valid Anagram
+// https://leetcode.com/problems/valid-anagram/
+func isAnagram(s string, t string) bool {
+	if len(s) != len(t) {
+		return false
+	}
+
+	mapA := buildCharMap(s)
+	mapB := buildCharMap(t)
+
+	for key, Acount := range mapA {
+		Bcount, ok := mapB[key]
+		if !ok {
+			return false
+		}
+		if Acount != Bcount {
+			return false
+		}
+	}
+
+	return true
+}
+
+func buildCharMap(s string) map[rune]int {
+	m := make(map[rune]int)
+
+	for _, char := range s {
+		if _, ok := m[char]; ok {
+			m[char]++
+		} else {
+			m[char] = 1
+		}
+	}
+
+	return m
+}

Week_01/id_29/LeetCode_257_29.go

@@ -0,0 +1,36 @@
+package main
+
+import "strconv"
+
+// LeetCode - 257. Binary Tree Paths
+// https://leetcode.com/problems/binary-tree-paths/
+func binaryTreePaths(root *TreeNode) []string {
+	if root == nil {
+		return nil
+	}
+
+	res := make([]string, 0, 16)
+
+	dfs("", root, &res)
+
+	return res
+}
+
+func dfs(path string, root *TreeNode, res *[]string) {
+	if path == "" {
+		path += strconv.Itoa(root.Val)
+	} else {
+		path += "->" + strconv.Itoa(root.Val)
+	}
+
+	if root.Left != nil {
+		dfs(path, root.Left, res)
+	}
+	if root.Right != nil {
+		dfs(path, root.Right, res)
+	}
+
+	if root.Left == nil && root.Right == nil {
+		*res = append(*res, path)
+	}
+}

Week_01/id_29/LeetCode_938_29.go

@@ -0,0 +1,19 @@
+package main
+
+// LeetCode - 938. Range Sum of BST
+// https://leetcode.com/problems/range-sum-of-bst/
+func rangeSumBST(root *TreeNode, L int, R int) int {
+	return dfs938(root, L, R)
+}
+
+func dfs938(root *TreeNode, L int, R int) int {
+	if root == nil {
+		return 0
+	}
+
+	if root.Val >= L && root.Val <= R {
+		return root.Val + dfs938(root.Left, L, R) + dfs938(root.Right, L, R)
+	}
+
+	return dfs938(root.Left, L, R) + dfs938(root.Right, L, R)
+}

Week_01/id_29/main.go

@@ -0,0 +1,16 @@
+package main
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func main() {
+
+}