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int sub_div(vector<int>& arr, int k) 
{
    map<int, int> mp;
    mp[0]++;
 
    int ans = 0, sum = 0;
    for(int i=0; i < arr.size(); i++)
    {
        sum += arr[i];
        int tmp = ((sum % k) + k) % k;      // NOTE - prefix sum can be -ve --> add k
 
        ans += mp[tmp];     
        mp[tmp]++;
    }
    return ans;
}

prog.cpp:1:13: error: ‘vector’ was not declared in this scope
 int sub_div(vector<int>& arr, int k)
             ^~~~~~
prog.cpp:1:20: error: expected primary-expression before ‘int’
 int sub_div(vector<int>& arr, int k)
                    ^~~
prog.cpp:1:31: error: expected primary-expression before ‘int’
 int sub_div(vector<int>& arr, int k)
                               ^~~
prog.cpp:1:36: error: expression list treated as compound expression in initializer [-fpermissive]
 int sub_div(vector<int>& arr, int k)
                                    ^

Standard output is empty