C++ If/Else语句问题

Question

我对这些If/Else语句的语法做错了什么我很确定它与我的大括号放置有关.我书中的所有例子都只包含非常原始/简单的例子(并不是说这段代码不简单; b/c就是这样).我想我的一般问题也是你如何将这两个单独的陈述分开.当我执行时,似乎两个独立的函数混合在一起.

  //
    tens = rand / 10;
    if (tens =  2){
            cout << "twenty ";
    else if (tens = 3)
            cout << "thirty ";
    else if (tens = 4)
            cout << "forty ";
    else if (tens = 5)
            cout << "fifty ";
    else if (tens = 6)
            cout << "sixty ";
    else if (tens = 7)
            cout << "seventy ";
    else if (tens = 8)
            cout << "eighty ";
    else if (tens = 9)
            cout << "ninety ";
    }

    //
    ones = rand % 10;
    if (ones =  0){
            cout << "\n";
    else if (ones = 1)
            cout << "one\n";
    else if (ones = 2)
            cout << "two\n";
    else if (ones = 3)
            cout << "three\n";
    else if (ones = 4)
            cout << "four\n";
    else if (ones = 5)
            cout << "five\n";
    else if (ones = 6)
            cout << "six\n";
    else if (ones = 7)
            cout << "seven\n";
    else if (ones = 8)
            cout << "eight\n";
    else if (ones = 9)
            cout << "nine\n";
    }

Answer 1

我认为,对于这个特殊的问题,如果 -甚至不需要!

我宁愿推荐这个解决方案:

const char *stens[] = {"", "", "twenty", "thirty", "forty", "fifty",
                               "sixty", "seventy", "eighty", "ninty"};
const char *sones[] = {"", "one", "two", "three", "four", "five", 
                               "six", "seven", "eigth", "nine"};

//make sure  0<= rand <= 99
 cout << stens[ rand / 10 ] << " " << sones[ rand % 10 ] << endl;

在线演示:http://www.ideone.com/K7HxS

至于if-else面临的问题,你正在使用赋值运算符,而不是平等,正如每个人已经指出的那样.

Answer 2

单个等号是一个赋值,而不是对相等性的测试.

你应该使用ones == N一些数字N.

你似乎没有正确使用大括号({和}),你的if陈述应该是这样的:

tens = rand / 10;
if (tens == 2){
        cout << "twenty ";
}else if (tens == 3){

注意在之前else和之后的括号3).

另外,我建议switch在这种情况下使用一个语句,它可能会导致一些更容易阅读和更易于管理的代码:

tens = rand / 10;
switch(tens){
  case 2: cout << "twenty "; break;
  case 3: cout << "thirty "; break;
  case 4: cout << "fourty "; break;
  // ...
  case 9: cout << "ninety "; break;
}