反转一个词：C ++

Question

I want to reverse a char string in c++. I wrote this code:

#include <iostream>
#include <string.h>

using namespace std;

int main(){
    char word[80] = "polymorphism";
    char rev[80];
    int i, j;
    int l;
    l = strlen(word);
    for(i = 0, j = l; i < l-1; i++, j--){
        word[j] = rev[i];
    }
    cout << rev << endl;
    return 0;
}

In terminal it shows some characters like this:

83???uH??? ... Something like this

Answer 1

Your character array rev is not zero terminated.

And istead of to write to rev you are writing to word.:)

    word[j] = rev[i];

The loop is also wrong due to condition

i < l-1;

There must be

i < l;

The program can look the following way

#include <iostream>
#include <cstring>

int main()
{
    char word[80] = "polymorphism";
    char rev[80];

    size_t n = std::strlen( word );

    size_t i = 0;
    for ( ; i < n; i++ ) rev[i] = word[n - i - 1];
    rev[i] = '\0';

    std::cout << word << std::endl;
    std::cout << rev << std::endl;

    return 0;
}

The program output is

polymorphism
msihpromylop

Take into account that you can do the same using standard algorithm std::reverse_copy declared in header <algorithm> . For example

#include <iostream>
#include <cstring>
#include <algorithm>

int main()
{
    char word[80] = "polymorphism";
    char rev[80];

    size_t n = std::strlen( word );

    *std::reverse_copy( word, word + n, rev ) = '\0';

    std::cout << word << std::endl;
    std::cout << rev << std::endl;

    return 0;
}

The program output is the same as above

polymorphism
msihpromylop

Answer 2

#include <iostream>
#include <string.h>

using namespace std;

int main(){
    char word[80] = "polymorphism";
    char rev[80] = {'\0'};
    int i = 0;
    int last = strlen(word) - 1;
    while(last >= 0) {
        rev[i] = word[last];
        i++;
        last--;
    }
    cout << rev << endl;
    return 0;
}

Answer 3

There are 3 changes I made to your code:
Change 1: Since string length is l , indexing will be from 0 to l-1 .
Change 2: rev will be storing the values from word , not the other way round.
Change 3: A proper string should be \\0 terminated.

#include <iostream>
#include <string.h>

using namespace std;

int main(){
char word[80] = "polymorphism";
char rev[80]="";
int i, j;
int l;
l = strlen(word);
for(i = 0, j = l-1; i < l; i++, j--){    //change 1
    rev[i] = word[j];                     // change 2   
}
rev[i]='\0';          // change 3 

cout<<rev;
return 0;
}

Working ideone link: http://ideone.com/kIqeNF