c++ - if 语句不比较我的字符串 c++ 中的数值

Question

作业是让用户输入具有一定要求的密码，例如长度、大写/小写字母和数字。当我尝试运行在字符串中添加数字数量的 for 循环时，它似乎跳过了 if 语句。

 #include <iostream>
 #include <cstring>
 #include <stdlib.h>
 using namespace std;

 int main()
 {
  const int LENGTH = 13;
  char str[LENGTH];
  int size = 0, k = 0, j = 0, r = 0;

 cout << "Enter a password." << endl;
 cout << "Must meet these requirements:" <<  endl;
 cout << "At least 10 and at most 12 characters." << endl;
 cout << "Any characters entered after 12 will be ignored." << endl;
 cout << "At least 2 lower case, and 2 upper case letters." << endl;
 cout << "At least 3, but no more than 5 numerical digits." << endl;
 cout << "No white spaces." << endl;

 cin.getline(str, LENGTH);

//Validating numerical values.
for (int z=0; z < 12; z++)
{
 if (str[z] >=0 && str[z] <=10)
{
 r++;
 }
}

 if (r<3 || r>5)
 {
cout << "Must have at least 3 but no more than 5 numerical digits."<<endl;
 exit (EXIT_FAILURE);
}

Answer 1

在您的代码中，您正在检查 0 到 10 之间的 ASCII 值，但您想要检查“0”和“9”之间的字符。您可以在 ASCII 表上检查这些字符的值并使用这些值:

if(str[z] >= 60 && str[z] <= 71)

或使用字符:

if(str[z] >='0' && str[z] <='9')