Refactor hasPairWithSum

Author: sheida-shab

Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js

@@ -1,21 +1,30 @@
 /**
  * Find if there is a pair of numbers that sum to a given target value.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
- *
+ * Time Complexity:before refactoring O(n²)- after refactoring O(n log n)
+ * Space Complexity:before refactoring O(1)- after refactoring O(1)
+ * Optimal Time Complexity:O(n log n)
+ * https://www.hellointerview.com/learn/code/two-pointers/overview
+ * The refactored solution first sorts the array, which takes O(n log n) time,
+ * and then uses the two-pointer technique to scan the array in a single pass (O(n)). The sorting step dominates the overall complexity.
  * @param {Array<number>} numbers - Array of numbers to search through
  * @param {number} target - Target sum to find
  * @returns {boolean} True if pair exists, false otherwise
  */
 export function hasPairWithSum(numbers, target) {
-  for (let i = 0; i < numbers.length; i++) {
-    for (let j = i + 1; j < numbers.length; j++) {
-      if (numbers[i] + numbers[j] === target) {
-        return true;
-      }
-    }
+  numbers.sort((a,b)=>a-b);
+  let left=0;
+  let right=numbers.length-1;
+  while (left<right) {
+    const current_sum=numbers[left]+numbers[right];
+    if (current_sum === target){
+      return true;}
+    if (current_sum<target){
+      left +=1;
+    } else {
+      right -=1;
+    }  
   }
   return false;
+
 }