[HAI] home work leetcode

lib/missingNumber/missingNumber.ts

@@ -0,0 +1,13 @@
+export function missingNumber(nums: number[]) {
+
+  let overallSum = 0;
+  for (let i = 0; i <= nums.length; i++) {
+    overallSum += i;
+  }
+
+  for (const num of nums) {
+    overallSum -= num;
+  }
+
+  return overallSum;
+};