C++ Primer（第五版）练习5.5

#include <iostream>#include <string>#include <vector>using namespace std;int main() {const vector<string> scores = { "F","D","C","B","A","A++" };string lettergrade;int grade;cin >> grade;if (grade < 60)lettergrade = scores[0];else{lettergrade = scores[(grade - 50) / 10];if (grade != 100)if (grade % 10 > 7)lettergrade += '+';elseif (grade % 10 < 3)lettergrade += '-';}cout << lettergrade << endl;system("pause");return 0;}