/* Helping the user called Cherish here: https://www.sololearn.com/Discuss/1216361/?ref=app Date: 15th April 2018. Explanation required, what is the value of sum, and why? See comments at the bottom of this file, for an explanation. */ #include using namespace std; int main() { int sum = 0; cout << "sum = " << sum << endl << endl; for (int i = 0; i < 5; i++) { cout << "i = " << i << endl << endl; for (int j = i - 1; j > 0; j--) { // J_LABEL cout << "sum = " << sum << endl; cout << "i = " << i << endl; cout << "j = i - 1 = " << i << " - 1 = " << i - 1 << endl; cout << endl; sum++; } } cout << "sum = " << sum << endl; return 0; } /* Note, this is far harder than it looks to work out! So don't be disheartened as a beginner. sum = 0 i = 0 j = i - 1 = -1 for (int j = i - 1; j > 0; j--) for (int j = -1; j > 0; j--) [code doesn't run inside this for loop this time] sum = 0 i = 1 j = i - 1 = 0 for (int j = i - 1; j > 0; j--) for (int j = 0; j > 0; j--) [code doesn't run inside this for loop this time] sum = 0 i = 2 j = i - 1 = 1 for (int j = i - 1; j > 0; j--) for (int j = 1; j > 0; j--) [code runs inside this loop once] ==> sum++ sum = 1 i = 3 j = i - 1 = 2 for (int j = i - 1; j > 0; j--) for (int j = 2; j > 0; j--) [code runs inside this loop once] ==> sum++ sum = 2 for (int j = 1; j > 0; j--) [code runs inside this loop again] ==> sum++ sum = 3 i = 4 j = i - 1 = 3 for (int j = i - 1; j > 0; j--) for (int j = 3; j > 0; j--) [code runs inside this loop once] ==> sum++ sum = 4 for (int j = 2; j > 0; j--) [code runs inside this loop once] ==> sum++ sum = 5 for (int j = 1; j > 0; j--) [code runs inside this loop once] ==> sum++ sum = 6 end of for loops. */

For Loop Sum Question