LeetCode Was HARD Until I Learned These 15 Patterns

When I first started solving problems on LeetCode, I felt like I was drowning in complexity. Some problems seemed unsolvable, and the sheer variety of challenges left me frustrated. However, over time, I discovered that LeetCode problems often follow certain patterns. Once I recognized these patterns, everything changed. I went from struggling through problems to solving them confidently and efficiently.

In this article, I’ll share the 15 patterns that helped me conquer LeetCode. If you’re stuck in a similar spot, understanding these patterns can significantly improve your problem-solving skills.

1. Two Pointers

The Two Pointers technique is a powerful strategy for working with arrays or strings. Typically used when the input is sorted or when you need to find pairs or subarrays.

Example: Find Two Numbers That Sum to a Target

function twoSum(nums, target) {
  let left = 0, right = nums.length - 1;
  while (left < right) {
    const sum = nums[left] + nums[right];
    if (sum === target) return [nums[left], nums[right]];
    if (sum < target) left++;
    else right--;
  }
  return [];
}

• Explanation: By starting with two pointers at the ends of the array, we can quickly find pairs that sum to the target in a sorted array.

2. Sliding Window