在C ++中的if语句中使用多个条件 [英] Using multiple conditions in an if statement in C++

问题描述

我正在尝试在C ++中创建一个复杂的if语句，这将使我免于编写一大堆if语句，我想知道下面的代码是否真的有意义或我忽略了错误。

I am trying to create a complex if statement in C++ that will save me from writing a whole bunch of if statements, I am wondering if this code below actually makes sense or I am overlooking an error.

if(input==choice) {
        cout << "Tie!" << endl;
}else if(input=="rock" && choice=="scissors"
     || input=="scissors" && choice=="paper"
     || input="paper" && choice=="rock") {
        cout << input " beats " << choice << ", you win!" << endl;
}else if(input=="rock" && choice=="paper"
    || input=="scissors" && choice=="rock"
    || input=="paper" && choice=="scissors"){
        cout << choice << " beats " << input << ", you lose!" << endl;
}

我想要实现的是：

"if input is x AND choice is y, OR if...."

基本上我正在测试多个if-and条件，以便在遇到任何if-and条件时执行一行代码。输出抛出不匹配'运算符||'错误。

Basically I'm testing multiple "if-and" conditions so that a single line of code will execute if it hits any of the if-and conditions. The output throws a "no match for 'operator||'" error.

推荐答案

你在输入错误输入=纸&&选择==摇滚），但我建议你修改代码而不是修复拼写错误。难怪你在这个巨大的条件下犯了错字。你有很多重复和混合逻辑与输出。如果您在包含上花费一些代码，则可以在代码中保存一些...

You have a typo in input="paper" && choice=="rock"), but instead of fixing the typo I would suggest you to fix the code. No wonder you made a typo in this giant block of conditions. You have lots of repetion and mixing logic with output. If you spend some lines on includes, you can save some on code...

#include <iostream>
#include <string>
#include <vector>
#include <utility>
#include <algorithm>

bool win(const std::string& input, const std::string& choice) {
    static const std::vector<std::pair<std::string, std::string>> wins = 
            { { "rock", "scissors" },
              { "scissors", "paper"  },
              { "paper", "rock" }
            };
    return std::find(wins.begin(), wins.end(), std::make_pair(input, choice))
        != wins.end();
}

int main() {
    std::string choice = "paper";
    std::string input = "scissors";
    if (win(choice, input)) { std::cout << "you win! \n"; }
    else                    { std::cout << "you lose! \n"; }
}

作为下一步，您应该消除所有字符串，例如使用枚举作为在评论中讨论过。

As next step you should eliminate all that strings, eg by using enums as discussed in the comments.

这篇关于在C ++中的if语句中使用多个条件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！