two sum solution

Author: nancyel

two-sum/nancyel.ts

@@ -0,0 +1,19 @@
+/**
+ * Time Complexity: O(n) (using a single pass with a hash map)
+ * (If a nested loop was used, it would be O(n^2))
+ */
+function twoSum(nums: number[], target: number): number[] {
+  const numAndIndex = new Map<number, number>();
+
+  for (let i = 0; i < nums.length; i++) {
+    const diff = target - nums[i];
+
+    if (numAndIndex.has(diff)) {
+      return [numAndIndex.get(diff)!, i];
+    }
+
+    numAndIndex.set(nums[i], i);
+  }
+
+  return [];
+}