1. Two Sum

Problem

Two Sum - LeetCodeLeetCode

Intuition

Time Complexity

Space Complexity

Solution

class Solution {
    public int[] twoSum(int[] nums, int target) {
        // n -> nums.length, number of elements in array
        // Time Complexity: O(n), to traverse the nums array
        // Space Complexity: O(n), to store the complements in hashmap

        // Create a HashMap to store the elements and their indices
        Map<Integer, Integer> map = new HashMap<>();

        // Iterate through the array
        for (int i = 0; i < nums.length; i++) {
            int complement = target - nums[i]; // Calculate the complement required to reach the target

            // Check if the complement is present in the map
            if (map.containsKey(complement)) {
                // Return the indices of the current element and its complement
                return new int[]{i, map.get(complement)};
            }

            // If the complement is not found, add the current element to the map with its index
            map.put(nums[i], i);
        }

        // If no solution is found, return null
        return null;
    }
}