c++ - 我的 for 循环不断循环并导致程序崩溃

Question

我正在尝试制作一个程序，该程序将接收字符串并输出该字符串的大写版本。我的代码可以工作，但是一旦它循环遍历字符串并更改它，它就会立即崩溃，我不完全确定为什么。这是我的两段代码。

/*This program is to intended to receive a string and return a version of it in all upper case*/    
 #include <iostream>
 #include <string>
 #include <locale>
 using namespace std;

 string toUpper ( string str)
  {     
    cout <<"\n";    //Puts spaces between the input and output

    for (int i=0; i<str.length(); i++;)
    std::cout << std::toupper(str[i]);   //A loop which goes through each digit of the    string
    break;

    cout <<"\n\n";   //Creates spaces after the output
    return str;
  }

/*This program calls a function to make a string in upper case*/
 #include <iostream>
 #include <string>
 #include <sstream>
 #include <locale>
 #include "toUpper1.h" //Calls the header file which contains the loop      
 using namespace std; 

int main () 
 {  
    cout<<"\nPlease type in a word\n\n";

    string input;   //Creates a variable of cin that can be used in the toUpper command 
    cin>>input; //Makes a user input command part of the declared variable 

    cout<<toUpper(input);       //The command that causes the user input string to be transformed into upper case   
    return 0;   
 }

Answer 1

您可以使用下面的代码将字符串变为大写

增强字符串算法:

#include <boost/algorithm/string.hpp>
#include <string>

std::string str = "Hello World";

boost::to_upper(str);

std::string newstr = boost::to_upper_copy("Hello World");

或者像这样使用

#include <algorithm>
#include <string>

std::string str = "Hello World";
std::transform(str.begin(), str.end(),str.begin(), ::toupper);