solution 2

#include <stdio.h>
#include <string.h>
int main()
{
    int i;
    char str[20], rev[20];
    FILE *fpr, *fpw;
    fpr = fopen("F:\\input.txt", "r");
    fpw = fopen("F:\\output.txt", "w");
    while(fscanf(fpr, "%s", str) != EOF)
    {
        strcpy(rev, str);
        strrev(rev);
        if(strcmp(str, rev) != 0)
        {
            fprintf(fpw, "NO ");
        }
        else
        {
            fprintf(fpw, "%s ", str);
        }
    }
    fclose(fpr);
    fclose(fpw);
    return 0;
}