umhCjP - 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);
    char *tmp = (char*)malloc(sizeof(char) * (len*2 + 1));

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

    tmp[len*2] = '\0';
    return tmp;
}

int main(){
    char nyuryoku[1024];
    scanf("%s", nyuryoku);

    char* kaibun = setPalindrome(nyuryoku);
    printf("%s -> %s\n", nyuryoku, kaibun);

    free(kaibun);
    return 0;
}