BinarySearch - Sum of Two Numbers

https://binarysearch.com/problems/Sum-of-Two-Numbers

Problem Statement

Given a list of numbers nums and a number k, return whether any two elements from the list add up to k. You may not use the same element twice.

Note: Numbers can be negative or 0.

Constraints

n ≤ 100,000 where n is the length of nums

Solution

Use unordered_map to store the complement. If it is found, return true. If not, update m[nums[i]].

bool solve(vector<int>& nums, int k) {
    unordered_map<int, int=""> m;
    for (int i = 0; i < nums.size(); i++) {
        if (m.count(k - nums[i])) return true;
        m[nums[i]] = i;
    }
    return false;
}