Why this IF statement doesn't print inside a loop

Question

Could you please help me out to understand why the If statement is not executing. Thank you for your time.

    void allPerfects (int a, int b){

     int minVal = minN(a, b);
     int maxVal = maxN(a, b);
     int sum =0;
     vector<int> v;

     while (minVal < maxVal){
        v.push_back(minVal);
        minVal++;
     }
     for (int i = 0; i < v.size() ;i++){        
         for (int j = 0; j < i; j++){
            sum += v[j];
         }
         if (sum == v[i]){
            printInt(v[i], false); printStr(" is a perfect number!", true);
         }
     }
    }

Answer 1

Even if there aren't any bugs in your code you'll only get a print out for:

allPerfects(a, b);

if there are consecutive integers a , a + 1 , ... , a + n that sum up to a + n + 1 < b .

This is only true for:

1 + 2 == 3

and

0 + 1 + 2 == 3

so a has to be 0 or 1 and b has to be greater than or equal to 4 .

Edit: But this will only happen if you reset your sum :

 for (int i = 0; i < v.size() ;i++){
     sum = 0;  // This line is missing.       
     for (int j = 0; j < i; j++){
        sum += v[j];
     }
     if (sum == v[i]){
        printInt(v[i], false); printStr(" is a perfect number!", true);
     }
 }