solve: missing number

Author: tolluset

missing-number/tolluset.ts

@@ -0,0 +1,25 @@
+/*
+ * TC: O(n)
+ * SC: O(1)
+ * */
+function missingNumber(nums: number[]): number {
+  const n = nums.length;
+
+  const sum = (n * (n + 1)) / 2;
+  const actualSum = nums.reduce((acc, curr) => acc + curr, 0);
+
+  if (sum === actualSum) {
+    return 0;
+  }
+
+  return sum - actualSum;
+}
+
+const t1 = missingNumber([3, 0, 1]);
+console.info("🚀 : tolluset.ts:3: t1=", t1); // 2
+
+const t2 = missingNumber([0, 1]);
+console.info("🚀 : tolluset.ts:6: t2=", t2); // 2
+
+const t3 = missingNumber([9, 6, 4, 2, 3, 5, 7, 0, 1]);
+console.info("🚀 : tolluset.ts:9: t3=", t3); // 8