C++ if/else/嵌套问题

Question

我正在尝试学习 c++，但我的 if/else 语句遇到了问题。 当我在不打开和关闭大括号的情况下嵌套它们时，我以为我把它们放下了，但我尝试使用大括号，但我得到了错误。

有人能指出什么是错误的以及如何解决它，而不仅仅是答案；那样我什么都学不到。

这是我的来源：

#include "stdafx.h"
#include <iostream>
using namespace std;

int main()
{
 signed long int RealNumber = 31710;
 int Guess;

 cout << "Lets see if you can guess my favorite number... \n";
 cout << "Type in a number and hit enter to see if you have guessed it correctly. \n";
 cout << "you should know this one Danielle. \n \n ";
 cin >> Guess;


 if (Guess == RealNumber)
 {
  cout << "Wow, you are amazing! \n";
  cout << "Would you like to be punched?";
 }
 else
 {
  if (Guess < RealNumber)
   cout << "The number is higher";
  else
   if (Guess > RealNumber)
    cout << "The number is lower";
   else
    cout << "That is impossible!"; //trying to make sure that if anthing but a number is entered that the program doesn't crash.
 }

}
 char f;  // used to make the program wait for input before closing. 
 cin >> f;

 return 0;

Answer 1

你有一个额外的大括号，上面写着-

char f; 
cin >> f; 

这个右大括号匹配你的主函数的初始大括号。

您在 if/else 嵌套中使用的支撑结构对我来说似乎很好。

这里有一个提示 - 对于每个左大括号，请立即键入右大括号，并为其添加注释。你不必永远使用这个“拐杖”，但作为一个学习编写代码的初学者，这可能会很有帮助。

第 1 步：

int main()
{
}//main 

第 2 步：

int main()
{
    int foo; 
    cin >> foo; 
    if (foo < 100)
    {
        //todo 
    }// if (foo < 100)
}//main

第 3 步：

int main()
{
    int foo; 
    cin >> foo; 
    if (foo < 100)
    {
        cout << "foo is too small";
        cin >> foo; 
        if (foo < 100)
        {
            //todo 
        } // if (foo < 100), inner if statement 
    }// if (foo < 100)
}//main

等等。

Answer 2

使用具有自动缩进功能的文本编辑器是个好主意。这可能会帮助您避免像这样的“简单”错误。

Answer 3

请看大卫的回答。我还想指出，通常情况下，您需要编写 if-else 代码，如下所示：

 if (Guess == RealNumber)
 {
   cout << "Wow, you are amazing! \n";
   cout << "Would you like to be punched?";
 }
 else if (Guess < RealNumber)
 {
   cout << "The number is higher";
 }
 else if (Guess > RealNumber)
 {
   cout << "The number is lower";
 }
 else
 {
    cout << "That is impossible!";
 }

或

 if (Guess == RealNumber)
 {
   cout << "Wow, you are amazing! \n";
   cout << "Would you like to be punched?";
 }
 else if (Guess < RealNumber)
   cout << "The number is higher";
 else if (Guess > RealNumber)
   cout << "The number is lower";
 else
    cout << "That is impossible!";

Answer 4

试试这个

#include <iostream>
using namespace std;

int main()
{
 signed long int RealNumber = 31710;
 int Guess;

 cout << "Lets see if you can guess my favorite number... \n";
 cout << "Type in a number and hit enter to see if you have guessed it correctly. \n";
 cout << "you should know this one Danielle. \n \n ";
 std::cin >> Guess;


 if (Guess == RealNumber)
 {
  cout << "Wow, you are amazing! \n";
  cout << "Would you like to be punched?";
 }
 else
 {
  if (Guess < RealNumber)
   cout << "The number is higher";
  else
   if (Guess > RealNumber)
    cout << "The number is lower";
   else
    cout << "That is impossible!"; //trying to make sure that if anthing but a number is entered that the program doesn't crash.
 }

 char f;  // used to make the program wait for input before closing. 
 std::cin >> f;

 return 0;
} // <-- this bracket was misplaced

您的 main() 括号放错了位置。

Answer 5

你应该使用{}，你有if-else链。编译器看不到您如何缩进 if-else（以“数字更高”开头），并将其视为一个扁平的 if-elseif-else。但是，在这种特殊情况下，我认为它不会给您带来问题。

Answer 6

尝试计算左大括号和右大括号。

Answer 7

删除#include <stdafx.h>（如果这是 Visual Studio 项目，请在项目设置中关闭“预编译头文件”）。

将您放置在 main 的结尾 } 大括号之后的语句移到该大括号之前。

你不能在函数之外有非声明语句。

干杯&hth。