C++ Primer（第五版）练习3.25

首先，先给出书中所示的利用下标运算符实现划分分数段的程序：

#include <iostream>#include <string>#include <vector>using namespace std;int main(){vector<unsigned> scores(11, 0);unsigned grade;while (cin >> grade)if (grade <= 100)++scores[grade / 10];for (auto c : scores)cout << c << " ";system("pause");return 0;}

题目中要求使用迭代器改写程序并实现完全相同的功能：

#include <iostream>#include <string>#include <vector>using namespace std;int main(){vector<unsigned> scores(11,0);unsigned grade;auto it = scores.begin();while (cin >> grade)if (grade <= 100)++*(it + grade / 10);for (auto a : scores)cout << a << " ";system("pause");return 0;}