missing number solution

Author: hyer0705

missing-number/hyer0705.ts

@@ -0,0 +1,22 @@
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+function missingNumber(nums: number[]): number {
+  const n = nums.length;
+
+  const expectedSum = (n * (n + 1)) / 2;
+  const currentSum = nums.reduce((acc, curr) => acc + curr, 0);
+
+  return expectedSum - currentSum;
+}
+
+// Time Complexity: O(n^2)
+// Space Complexity: O(1)
+function missingNumber(nums: number[]): number {
+  const n = nums.length;
+
+  for (let i = 0; i <= n; i++) {
+    if (!nums.includes(i)) return i;
+  }
+
+  return -1;
+}