add new solutions

solutions/13/q1318/solution.go

@@ -0,0 +1,28 @@
+package q1318
+
+func minFlips(a int, b int, c int) int {
+	aorb := a | b
+	flips := 0
+
+	p := 1
+	for p <= aorb || p <= c {
+		switch {
+		case c|p == c && aorb|p != aorb:
+			flips++ // c has the bit
+
+		case c|p != c && aorb|p == aorb:
+			if a|p == a {
+				flips++ // a has the bit
+			}
+			if b|p == b {
+				flips++ // b has the bit
+			}
+		}
+
+		p <<= 1
+	}
+
+	return flips
+}
+
+var _ = minFlips

solutions/13/q1372/solution.go

@@ -0,0 +1,34 @@
+package q1372
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func zigZagLen(node *TreeNode, isLeft bool, curLen int) int {
+	if node == nil {
+		return 0
+	}
+	var l, r int
+	if isLeft {
+		l = zigZagLen(node.Left, true, 1)
+		r = zigZagLen(node.Right, false, curLen+1)
+	} else {
+		l = zigZagLen(node.Left, true, curLen+1)
+		r = zigZagLen(node.Right, false, 1)
+	}
+	return max(curLen, l, r)
+}
+
+func longestZigZag(root *TreeNode) int {
+	if root == nil {
+		return 0
+	}
+	return max(
+		zigZagLen(root.Left, true, 1),
+		zigZagLen(root.Right, false, 1),
+	)
+}
+
+var _ = longestZigZag