Many array problems look like they need nested loops. That means O(n²) time. But with one simple idea — Two Pointers — you can often reduce it to O(n). What is Two Pointer Technique? Instead of using one loop, you use two indices (pointers): From opposite ends Or moving in the same direction Helps reduce unnecessary work Example 1: Two Sum (Sorted Array) public static int[] twoSumSorted(int[] arr, int target) { int left = 0, right = arr.length - 1; while (left < right) { int sum = arr[left] + arr[right]; if (sum == target) return new int[]{left, right}; else if (sum < target) left++; else right--; } return new int[]{-1, -1}; Enter fullscreen mode Exit fullscreen mode } Idea: If sum is small → move left If sum is large → move right Example 2: Remove Duplicates public static int removeDuplicates(int[] arr) { if (arr.length == 0) return 0; int writeIndex = 1; for (int readIndex = 1; readIndex < arr.length; readIndex++) { if (arr[readIndex] != arr[readIndex - 1]) { arr[writeIndex++] = arr[readIndex]; }…