028_Hamming.c

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#include <stdio.h>
#include <math.h>
 
#define MC 2048
#define l2 log(2)
 
int main(int argc, char *argv[])
{
    char str[MC], strP[MC];
    int i, j, k, nc, nP;
    i=0;
    do{
        str[i++] = getc(stdin);
    }while(str[i-1]!=10);
    str[i-1] = '\0';
    nc = i-1;
    nP = log(nc+log(nc)/l2+1)/l2+1;
    printf("%s(%d, %d)\n", str, nc, nP);
    for(i=0, j=1, k=0; i<nc+nP; i++)
    {
        if((i+1)!=j)
            strP[i] = str[k++];
        else
        {
            strP[i] = 0;
            j<<=1;
        }
    }
    for(i=0, j=1; i<nP; i++)
    {
        for(k=j; k<=(nc+nP); k++)
            if(((k-j)%(2*j))<j)
                strP[j-1]^=strP[k-1];
//          printf("%d\t", ((k-j)%(2*j))<j);
//      printf("\n");
        j<<=1;
    }
    strP[nc+nP] = '\0';
    for(i=0; i<nc+nP; i++)
        printf("%d\n", strP[i]);
    printf("%s\n", strP);
    return 0;
}