feat: add ts solution to lc problem: No.0137

Author: rain84

solution/0100-0199/0137.Single Number II/README.md

@@ -343,4 +343,24 @@ impl Solution {
 
 <!-- solution:end -->
 
+<!-- solution:start -->
+
+### Solution 1: Set + Math
+
+<!-- tabs:start -->
+
+#### TypeScript
+
+```ts
+function singleNumber(nums: number[]): number {
+    const sumOfUnique = [...new Set(nums)].reduce((a, b) => a + b, 0);
+    const sum = nums.reduce((a, b) => a + b, 0);
+    return (sumOfUnique * 3 - sum) / 2;
+}
+```
+
+<!-- tabs:end -->
+
+<!-- solution:end -->
+
 <!-- problem:end -->

solution/0100-0199/0137.Single Number II/README_EN.md

@@ -334,4 +334,24 @@ impl Solution {
 
 <!-- solution:end -->
 
+<!-- solution:start -->
+
+### Solution 1: Set + Math
+
+<!-- tabs:start -->
+
+#### TypeScript
+
+```ts
+function singleNumber(nums: number[]): number {
+    const sumOfUnique = [...new Set(nums)].reduce((a, b) => a + b, 0);
+    const sum = nums.reduce((a, b) => a + b, 0);
+    return (sumOfUnique * 3 - sum) / 2;
+}
+```
+
+<!-- tabs:end -->
+
+<!-- solution:end -->
+
 <!-- problem:end -->

solution/0100-0199/0137.Single Number II/Solution3.ts

@@ -0,0 +1,5 @@
+function singleNumber(nums: number[]): number {
+    const sumOfUnique = [...new Set(nums)].reduce((a, b) => a + b, 0);
+    const sum = nums.reduce((a, b) => a + b, 0);
+    return (sumOfUnique * 3 - sum) / 2;
+}