1k4sTs - Online C Compiler & Debugging Tool

#include <stdio.h>
#include <stdlib.h>

int myStrlen(char s[]){
    int i;
    for(i=0; s[i] != '\0'; i++);
    return i;
}

char *setPalindrome(char s[]){
    int len = myStrlen(s);
    int newLen = len * 2;

    char *tmp = (char *)malloc((newLen + 1) * sizeof(char));

    int i;

    for(i = 0; i < len; i++){
        tmp[i] = s[i];
    }

    for(i = 0; i < len; i++){
        tmp[len + i] = s[len - 1 - i];
    }

    tmp[newLen] = '\0';

    return tmp;
}

int main(){
    char nyuryoku[1024]; //入力
    char *kaibun;        //回文を受け取る

    scanf("%s", nyuryoku);
    kaibun = setPalindrome(nyuryoku);

    printf("%s\n  -> %s\n", nyuryoku, kaibun);

    free(kaibun);
    return 0;
}