217. Contains Duplicate

Problem Statement

• Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

Approach

• Set -> if set size == vector size (no duplicates) ; else duplicates
• HashMap -> insert elements with value increment for each entry.
  • Iterate map manually for all keys using ForEach, if any key has >1 value; return true else false

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_set<int> st;
        for(auto a : nums)
            st.insert(a);

        if(st.size() == nums.size())
            return false;
        return true;
    }
};