Paridade.c

#include <stdio.h>
#include <string.h>

#define MAX 1024

int numOcc(char * str, char srch) {
    int i, Count = 0;
    for(i = 0; i < strlen(str); i++) {
        if(str[i] == srch)
            Count++;
    }

    return Count;
}

void toBin(char * num, char * dest) {
    unsigned int pNum = atoi(num);
    int i, bin[MAX];
    for(i = 0; i < MAX; i++)
        bin[i] = -1;

    i = MAX - 1;

    strcpy(dest, "");

    while(pNum > 0) {
        bin[i] = pNum%2;
        pNum /= 2;
        i--;
    }

    for(i = 0; i < MAX; i++) {
        if(bin[i] == -1)
            continue;

        char buffer[2];
        sprintf(buffer, "%d", bin[i]);

        strcat(dest, buffer);
    }
}

int main(void) {
    int i;
    char nums[MAX][11];

    for(i = 0; i < MAX; i++)
        strcpy(nums[i], "");

    i = 0;
    while(1) {
        char aux[10 + 1];
        scanf("%s", aux);

        if(strcmp(aux, "0") == 0)
            break;

        strcpy(nums[i], aux);
        i++;
    }

    i = 0;
    while(1) {
        if(strcmp(nums[i], "") == 0)
            break;

        char Bin[MAX];
        toBin(nums[i], Bin);

        printf("The parity of %s is %d (mod 2).\n", Bin, numOcc(Bin, '1'));
        i++;
    }

    return 0;
}