字符串反向程序崩溃

Question

I am making a program that is reversing a given string. but i don't know why my program is crashing. Help will be highly appreciated instead of criticism. Thanks!

#include <iostream>
#include <string>

using namespace std;

string reverse(string );

int main()
{
    string str;
    cout << "Enter a string"<<endl;
    getline (cin, str);
    reverse(str);
}

string reverse (string str)
{
    string str1;
    for(int i = str.length(); i >= 0; i--)
    {
        str1[i] = str[i];
    } 
    return str1;
}

Answer 1

There are at least three problems in your code:

1. You need to have a string with a length prior to accessing it with [], especially when writing to it.
2. The code is trying to access out of bounds.
3. The algorithm is just copying the string in reverse order, not reversing the string itself.

Implementation left as an excercise to the reader.

Answer 2

You do not need to reinvent the wheel, use an algorithm!

#include <algorithm>
#include <iostream>
#include <string>

int main()
{
    string str;
    cout << "Enter a string"<<endl;
    getline (cin, str);
    std::reverse(str.begin(), str.end());
}

You can read more about std::reverse on cppreference.com .

Answer 3

str.length()为您提供字符串的长度，但是当您将其用作数组的索引时，您最终会遇到数组越界错误

Answer 4

#include <algorithm>
#include <string>

void reverse_in_place(std::string &str) {
  std::reverse(str.begin(), str.end());
}
std::string copy_and_reverse(std::string str) {
  std::reverse(str.begin(), str.end());
  return str;
}