Hash Map

Q1: Find the Difference of Two Arrays

class Solution {
public:
    bool uniqueOccurrences(vector<int>& arr) {
        unordered_map<int, int> mp;
        unordered_map<int, int> mp2;

        for(int i = 0; i < arr.size(); i++) { 
            if(mp.find(arr[i]) != mp.end()) 
                mp[arr[i]]++;
            else
                mp[arr[i]] = 1;
        }

        for(auto it = mp.begin(); it != mp.end(); it++) {
            if(mp2.find(it->second) != mp2.end())
                mp2[it->second]++;
            else
                mp2[it->second] = 1;
        }

        for(auto it = mp2.begin(); it != mp2.end(); it++) {
            if(mp2[it->first] >= 2) 
                return false;
        }

        return true;
    }
};

Q2: Equal Row and Column Pairs 79/80 :)

class Solution {
public:
    int equalPairs(vector<vector<int>>& grid) {
        
        unordered_map<int, int> rowMap;
        unordered_map<int, int> colMap;

        for(int i = 0; i < grid[0].size(); i++) {
            int sum = 0;
            
            for(int j = 0; j < grid[0].size(); j++) sum += grid[i][j];
            rowMap[i] = sum;
        }
        
        for(int i = 0; i < grid[0].size(); i++) {
            int sum = 0;  
            
            for(int j = 0; j < grid[0].size(); j++) sum += grid[j][i];
            colMap[i] = sum;
        }

        int countSum = 0;

        for(int i = 0; i < grid[0].size(); i++) {

            for(int j = 0; j < grid[0].size(); j++) {
                
                if(rowMap[i] == colMap[j]) {
                    bool isEqual = true;

                    for(int k = j; k < grid[0].size(); k++) {

                        if(grid[i][k] != grid[k][j]) isEqual = false;
                        
                    }
                    if(isEqual) countSum++;

                }   
            }
        }

        return countSum;
    }
};