Two Sum Problem [Leetcode]

Difficulty – Easy

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9.

Because nums[0] + nums[1] = 2 + 7 = 9,

return [0, 1].

Two Sum Problem Solution

The best way to solve this problem by using Hashmap in Java

public int[] twoSum(int[] nums, int target){
    Map<Integer, Integer> map = new Hashmap<>();
    for(int i=0; i<nums.length; i++){
        int complement = target - nums[i];
        if(map.containsKey(complement)){
            return new int[] { map.get(complement), i};
        }
        map.put(nums[i], i);
    }
    throw new IllegalArgumentException("No two sum solution");
}

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