uri1026.c

/********************
 * Resolução para o problema: https://www.urionlinejudge.com.br/judge/pt/problems/view/1026
 * Por Luiz Felipe - https://github.com/Silva97
 ********************/

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

char* utostr(char *str, unsigned int n);
char  output[BUFSIZ];

int main(){
    unsigned int a, b;
    char input[65], *p, *outp = output;

    while(fgets(input, 64, stdin) != NULL){
        a = strtoul(input, &p, 10);
        if(p == input) break;

        b        = strtoul(p + 1, NULL, 10);
        outp     = utostr(outp, a ^ b);
        *outp++  = '\n';
        *outp    = '\0';
        input[0] = '\0';

        if(outp - output > BUFSIZ - 128){
            printf("%s", output);
            output[0] = '\0';
            outp      = output;
        }
    }

    if(output[0])
        printf("%s", output);
    return 0;
}

char* utostr(char *str, unsigned int n){
    char *ptr = str, *p, c;

    do {
        *ptr++ = (n % 10) + '0';
    } while(n = n / 10);

    *ptr = '\0';
    p    = ptr - 1;

    while(str < p){
        c      = *str;
        *str++ = *p;
        *p--   = c;
    }

    return ptr;
}