add new solutions

solutions/0/q2/solution.go

@@ -0,0 +1,35 @@
+package q2
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
+	retRoot := &ListNode{}
+
+	p := retRoot
+	carry := 0
+	for l1 != nil || l2 != nil {
+		val := carry
+		if l1 != nil {
+			val += l1.Val
+			l1 = l1.Next
+		}
+		if l2 != nil {
+			val += l2.Val
+			l2 = l2.Next
+		}
+
+		carry, val = val/10, val%10
+		node := &ListNode{Val: val}
+		p.Next = node
+		p = node
+	}
+	if carry > 0 {
+		p.Next = &ListNode{Val: carry}
+	}
+	return retRoot.Next
+}
+
+var _ = addTwoNumbers

solutions/0/q72/solution.go

@@ -0,0 +1,36 @@
+package q72
+
+func make2d[T any](rows, cols int) [][]T {
+	alloc := make([]T, rows*cols)
+	ret := make([][]T, rows)
+	for i := range ret {
+		ret[i] = alloc[cols*i : cols*(i+1)]
+	}
+	return ret
+}
+
+func minDistance(word1 string, word2 string) int {
+	minDists := make2d[int](len(word1)+1, len(word2)+1)
+
+	for i1 := range len(word1) {
+		minDists[i1+1][0] = i1 + 1
+	}
+	for i2 := range len(word2) {
+		minDists[0][i2+1] = i2 + 1
+	}
+
+	for i1 := 1; i1 <= len(word1); i1++ {
+		for i2 := 1; i2 <= len(word2); i2++ {
+			if word1[i1-1] == word2[i2-1] {
+				minDists[i1][i2] = minDists[i1-1][i2-1]
+			} else {
+				minDists[i1][i2] = min(
+					minDists[i1-1][i2], minDists[i1][i2-1], minDists[i1-1][i2-1],
+				) + 1
+			}
+		}
+	}
+	return minDists[len(word1)][len(word2)]
+}
+
+var _ = minDistance

solutions/0/q74/solution.go

@@ -0,0 +1,23 @@
+package q74
+
+func searchMatrix(matrix [][]int, target int) bool {
+	w, h := len(matrix[0]), len(matrix)
+	idx := func(i int) (int, int) { return i / w, i % w }
+
+	l, r := 0, w*h
+	for l < r {
+		m := (l + r) / 2
+		row, col := idx(m)
+		switch {
+		case matrix[row][col] == target:
+			return true
+		case matrix[row][col] < target:
+			l = m + 1
+		default:
+			r = m
+		}
+	}
+	return false
+}
+
+var _ = searchMatrix

solutions/1/q103/solution.go

@@ -0,0 +1,55 @@
+package q103
+
+import "slices"
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func zigzagLevelOrder(root *TreeNode) [][]int {
+	ret := [][]int{}
+	if root == nil {
+		return ret
+	}
+
+	dpth := 1
+	buf := make([]int, 512)
+	row := buf[:0]
+
+	type qElem struct {
+		depth int
+		node  *TreeNode
+	}
+	queue := make([]qElem, 0, 256)
+	queue = append(queue, qElem{depth: 1, node: root})
+	for ; len(queue) > 0; queue = queue[1:] {
+		c := queue[0]
+		if c.depth > dpth {
+			if dpth%2 == 0 {
+				slices.Reverse(row)
+			}
+			ret = append(ret, make([]int, len(row)))
+			copy(ret[len(ret)-1], row)
+
+			dpth = c.depth
+			row = buf[:0]
+		}
+
+		row = append(row, c.node.Val)
+		if c.node.Left != nil {
+			queue = append(queue, qElem{depth: c.depth + 1, node: c.node.Left})
+		}
+		if c.node.Right != nil {
+			queue = append(queue, qElem{depth: c.depth + 1, node: c.node.Right})
+		}
+	}
+	if dpth%2 == 0 {
+		slices.Reverse(row)
+	}
+	ret = append(ret, row)
+	return ret
+}
+
+var _ = zigzagLevelOrder

solutions/1/q106/solution.go

@@ -0,0 +1,26 @@
+package q106
+
+import "slices"
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func buildTree(inorder []int, postorder []int) *TreeNode {
+	if len(inorder) == 0 {
+		return nil
+	}
+
+	val := postorder[len(postorder)-1]
+	pos := slices.Index(inorder, val)
+
+	return &TreeNode{
+		Val:   val,
+		Left:  buildTree(inorder[0:pos], postorder[:pos]),
+		Right: buildTree(inorder[pos+1:], postorder[pos:len(postorder)-1]),
+	}
+}
+
+var _ = buildTree

solutions/1/q117/solution.go

@@ -0,0 +1,34 @@
+package q117
+
+type Node struct {
+	Val   int
+	Left  *Node
+	Right *Node
+	Next  *Node
+}
+
+func walk(node *Node, depth int, depths *[]*Node) {
+	if node == nil {
+		return
+	}
+
+	if depth > len(*depths) {
+		*depths = append(*depths, nil)
+	}
+	if (*depths)[depth-1] != nil {
+		(*depths)[depth-1].Next = node
+	}
+	(*depths)[depth-1] = node
+
+	walk(node.Left, depth+1, depths)
+	walk(node.Right, depth+1, depths)
+}
+
+func connect(root *Node) *Node {
+	depths := []*Node{}
+	walk(root, 1, &depths)
+
+	return root
+}
+
+var _ = connect

solutions/1/q118/solution.go

@@ -0,0 +1,26 @@
+package q118
+
+func generate(numRows int) [][]int {
+	buf := make([]int, numRows*(1+numRows)/2)
+	p := 0
+	take := func(n int) []int {
+		ret := buf[p : p+n]
+		p = p + n
+		return ret
+	}
+
+	ret := make([][]int, 0, numRows)
+
+	for i := 1; i <= numRows; i++ {
+		row := take(i)
+		row[0] = 1
+		row[len(row)-1] = 1
+		for j := 1; j < len(row)-1; j++ {
+			row[j] = ret[i-2][j-1] + ret[i-2][j]
+		}
+		ret = append(ret, row)
+	}
+	return ret
+}
+
+var _ = generate

solutions/1/q129/solution.go

@@ -0,0 +1,33 @@
+package q129
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func sumNums(node *TreeNode, prefix int) int {
+	prefix = prefix*10 + node.Val
+
+	if node.Left == nil && node.Right == nil {
+		return prefix
+	}
+
+	sum := 0
+	if node.Left != nil {
+		sum += sumNums(node.Left, prefix)
+	}
+	if node.Right != nil {
+		sum += sumNums(node.Right, prefix)
+	}
+	return sum
+}
+
+func sumNumbers(root *TreeNode) int {
+	if root == nil {
+		return 0
+	}
+	return sumNums(root, 0)
+}
+
+var _ = sumNumbers

solutions/1/q148/solution.go

@@ -0,0 +1,32 @@
+package q148
+
+import "slices"
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func sortList(head *ListNode) *ListNode {
+	if head == nil {
+		return nil
+	}
+
+	arr := []*ListNode{}
+	for head != nil {
+		arr = append(arr, head)
+		head = head.Next
+	}
+
+	slices.SortFunc(arr, func(a, b *ListNode) int { return a.Val - b.Val })
+	for i := range arr {
+		if i == len(arr)-1 {
+			arr[i].Next = nil
+		} else {
+			arr[i].Next = arr[i+1]
+		}
+	}
+	return arr[0]
+}
+
+var _ = sortList

solutions/1/q173/solution.go

@@ -0,0 +1,65 @@
+package q173
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+type stackElem struct {
+	state uint8 // 0, 1, 2, 3
+	node  *TreeNode
+}
+
+type BSTIterator struct {
+	stack []stackElem
+	next  *TreeNode
+}
+
+func Constructor(root *TreeNode) BSTIterator {
+	return BSTIterator{stack: []stackElem{{node: root}}}
+}
+
+func (it *BSTIterator) Next() int {
+	it.findNext()
+	ret := it.next.Val
+	it.next = nil
+	return ret
+}
+
+func (it *BSTIterator) HasNext() bool {
+	it.findNext()
+	return it.next != nil
+}
+
+func (it *BSTIterator) findNext() {
+	for it.next == nil && len(it.stack) > 0 {
+		c := &it.stack[len(it.stack)-1]
+		c.state++
+
+		switch c.state - 1 {
+		case 0: // init
+			if c.node.Left != nil {
+				it.stack = append(it.stack, stackElem{node: c.node.Left})
+			}
+
+		case 1: // left processed
+			it.next = c.node
+
+		case 2: // middle processed
+			if c.node.Right != nil {
+				it.stack = append(it.stack, stackElem{node: c.node.Right})
+			}
+
+		case 3: // right processed
+			it.stack = it.stack[:len(it.stack)-1]
+		}
+	}
+}
+
+/**
+ * Your BSTIterator object will be instantiated and called as such:
+ * obj := Constructor(root);
+ * param_1 := obj.Next();
+ * param_2 := obj.HasNext();
+ */

solutions/2/q201/solution.go

@@ -0,0 +1,21 @@
+package q201
+
+func rangeBitwiseAnd(left int, right int) int {
+	ret := left & right
+	for i := ret + 1; i < right; {
+		ret &= i
+		if ret == 0 {
+			return 0
+		}
+
+		// Find first non-zero bit
+		t := 1
+		for i|t != i {
+			t <<= 1
+		}
+		i += t
+	}
+	return ret
+}
+
+var _ = rangeBitwiseAnd

solutions/2/q210/solution.go

@@ -0,0 +1,34 @@
+package q210
+
+func findOrder(numCourses int, prerequisites [][]int) []int {
+	ndeps := make([]int, numCourses)
+	revDeps := make([][]int, numCourses)
+	ret := make([]int, 0, numCourses)
+
+	for i := range prerequisites {
+		c, dep := prerequisites[i][0], prerequisites[i][1]
+		ndeps[c]++
+		revDeps[dep] = append(revDeps[dep], c)
+	}
+
+	for i := range ndeps {
+		if ndeps[i] == 0 {
+			ret = append(ret, i)
+		}
+	}
+	for i := 0; i < len(ret); i++ {
+		for _, c := range revDeps[ret[i]] {
+			ndeps[c]--
+			if ndeps[c] == 0 {
+				ret = append(ret, c)
+			}
+		}
+	}
+
+	if len(ret) != numCourses {
+		return nil
+	}
+	return ret
+}
+
+var _ = findOrder

solutions/2/q289/solution.go

@@ -0,0 +1,41 @@
+package q289
+
+func countLiveNeighbors(board [][]int, row, col int) int {
+	cnt := 0
+	for r := row - 1; r <= row+1; r++ {
+		for c := col - 1; c <= col+1; c++ {
+			if r == row && c == col || r < 0 || c < 0 || r >= len(board) || c >= len(board[0]) {
+				continue
+			}
+			cnt += board[r][c] & 1
+		}
+	}
+	return cnt
+}
+
+func gameOfLife(board [][]int) {
+	for r := range board {
+		for c := range board[r] {
+			neighbors := countLiveNeighbors(board, r, c)
+			if board[r][c]&1 == 1 {
+				switch {
+				case neighbors < 2 || neighbors > 3:
+					// die
+				default:
+					board[r][c] |= 2 // survive
+				}
+			} else if neighbors == 3 {
+				board[r][c] |= 2 // birth
+			}
+		}
+	}
+
+	// Next generation
+	for r := range board {
+		for c := range board[r] {
+			board[r][c] >>= 1
+		}
+	}
+}
+
+var _ = gameOfLife

solutions/29/q2943/solution.go

@@ -0,0 +1,27 @@
+package q2943
+
+import "slices"
+
+func longestSeq(arr []int) int {
+	max_ := 1
+	len_ := 1
+	for i := 1; i < len(arr); i++ {
+		if arr[i] == arr[i-1]+1 {
+			len_++
+		} else {
+			len_ = 1
+		}
+		max_ = max(len_, max_)
+	}
+	return max_
+}
+
+func maximizeSquareHoleArea(n, m int, hBars, vBars []int) int {
+	slices.Sort(hBars)
+	slices.Sort(vBars)
+
+	edge := min(longestSeq(hBars), longestSeq(vBars)) + 1
+	return edge * edge
+}
+
+var _ = maximizeSquareHoleArea

solutions/3/q373/solution.go

@@ -0,0 +1,46 @@
+package q373
+
+import "container/heap"
+
+type MHeap [][]int
+
+func (m *MHeap) Len() int { return len(*m) }
+
+func (m *MHeap) Less(i int, j int) bool {
+	return (*m)[i][0]+(*m)[i][1] > (*m)[j][0]+(*m)[j][1]
+}
+
+func (m *MHeap) Pop() any {
+	ret := (*m)[len(*m)-1]
+	*m = (*m)[:len(*m)-1]
+	return ret
+}
+
+func (m *MHeap) Push(x any) {
+	elem, _ := x.([]int)
+	*m = append(*m, elem)
+}
+
+func (m *MHeap) Swap(i int, j int) { (*m)[i], (*m)[j] = (*m)[j], (*m)[i] }
+
+func kSmallestPairs(nums1 []int, nums2 []int, k int) [][]int {
+	h := make(MHeap, 0, k)
+	for i := range min(k, len(nums1)) {
+		for j := range min(k, len(nums2)) {
+			if h.Len() < k {
+				heap.Push(&h, []int{nums1[i], nums2[j]})
+				continue
+			}
+
+			if nums1[i]+nums2[j] >= h[0][0]+h[0][1] {
+				break
+			}
+			h[0][0], h[0][1] = nums1[i], nums2[j]
+			heap.Fix(&h, 0)
+		}
+	}
+
+	return h
+}
+
+var _ = kSmallestPairs

solutions/34/q3453/solution.go

@@ -0,0 +1,41 @@
+package q3453
+
+import (
+	"math"
+	"slices"
+)
+
+func separateSquares(squares [][]int) float64 {
+	slices.SortFunc(squares, func(a, b []int) int { return a[1] - b[1] })
+	var totalArea float64
+	var maxY int
+	for i := range squares {
+		totalArea += math.Pow(float64(squares[i][2]), 2)
+		maxY = max(maxY, squares[i][1]+squares[i][2])
+	}
+
+	target := totalArea / 2
+
+	// Binary search
+	var l, r float64 = 0, float64(maxY)
+	for range 64 {
+		m := (l + r) / 2
+
+		var area float64
+		for i := range squares {
+			y, l := float64(squares[i][1]), float64(squares[i][2])
+			if y >= m {
+				break
+			}
+			area += l * min(l, m-y)
+		}
+		if area < target {
+			l = m
+		} else {
+			r = m
+		}
+	}
+	return l
+}
+
+var _ = separateSquares

solutions/34/q3454/solution.go

@@ -0,0 +1,85 @@
+package q3454
+
+import (
+	"math"
+	"slices"
+)
+
+type void struct{}
+
+func calcLengthAtY(squares [][]int) [][2]int {
+	vertIdx := make([][2]int, len(squares)*2)
+	for i := range squares {
+		vertIdx[i*2] = [2]int{squares[i][1], i}
+		vertIdx[i*2+1] = [2]int{squares[i][1] + squares[i][2], i}
+	}
+	slices.SortFunc(vertIdx, func(a, b [2]int) int { return a[0] - b[0] })
+
+	curSq := map[int]void{}
+	curLenBuf := make([][2]int, len(squares))
+
+	calcLen := func() int {
+		curLen := 0
+		curLenBuf = curLenBuf[:0]
+		for i := range curSq {
+			l := squares[i][0]
+			r := l + squares[i][2]
+			curLenBuf = append(curLenBuf, [2]int{l, r})
+		}
+		slices.SortFunc(curLenBuf, func(a, b [2]int) int { return a[0] - b[0] })
+		r := math.MinInt
+		for i := range curLenBuf {
+			if curLenBuf[i][0] < r {
+				curLen += max(0, curLenBuf[i][1]-r)
+			} else {
+				curLen += curLenBuf[i][1] - curLenBuf[i][0]
+			}
+			r = max(r, curLenBuf[i][1])
+		}
+		return curLen
+	}
+
+	ret := make([][2]int, 0, len(squares)*2)
+	for i := 0; i < len(vertIdx); {
+		curY := vertIdx[i][0]
+		for ; i < len(vertIdx) && vertIdx[i][0] == curY; i++ {
+			sq := vertIdx[i][1]
+			if _, ok := curSq[sq]; ok {
+				delete(curSq, sq)
+			} else {
+				curSq[sq] = void{}
+			}
+		}
+
+		ret = append(ret, [2]int{curY, calcLen()})
+	}
+	return ret
+}
+
+func separateSquares(squares [][]int) float64 {
+	lenAtY := calcLengthAtY(squares)
+
+	totalArea := 0
+	for i := 0; i < len(lenAtY)-1; i++ {
+		totalArea += lenAtY[i][1] * (lenAtY[i+1][0] - lenAtY[i][0])
+	}
+
+	var area int
+	for i := 0; i < len(lenAtY)-1; i++ {
+		y, nextY := lenAtY[i][0], lenAtY[i+1][0]
+		l := lenAtY[i][1]
+
+		areaT := (nextY-y)*l + area
+		switch {
+		case areaT*2 == totalArea:
+			return float64(nextY)
+		case areaT*2 > totalArea:
+			needed := float64(totalArea-area*2) / 2
+			return float64(y) + needed/float64(l)
+		}
+		area = areaT
+	}
+	return -1
+}
+
+var _ = separateSquares

solutions/4/q435/solution.go

@@ -0,0 +1 @@
+package q435