add sol

leetcode/268.MissingNumber/missingNumber.go

@@ -0,0 +1,39 @@
+// https://leetcode.com/problems/missing-number/
+
+package main
+
+import (
+	"fmt"
+)
+
+func missingNumber(nums []int) int {
+	n := len(nums)
+	sum := 0
+	for _, v := range nums {
+		sum += v
+	}
+
+	return n*(n+1)/2 - sum
+}
+
+func missingNumber1(nums []int) int {
+	n := len(nums)
+	m := make([]bool, n+1)
+
+	for _, v := range nums {
+		m[v] = true
+	}
+
+	for i, exists := range m {
+		if !exists {
+			return i
+		}
+	}
+
+	return 0
+}
+
+func main() {
+	nums := []int{9, 6, 4, 2, 3, 5, 7, 0, 1}
+	fmt.Println(missingNumber1(nums))
+}