// https://en.wikipedia.org/wiki/Berlekamp%E2%80%93Massey_algorithm)
#include <stdio.h>
int main(void) {
    int s[]={1,1,0,0,0,0,1,0,1,0,0,1,1}; // the bits of the stream
    #define n (sizeof(s)/sizeof(*s))     // how many there are
    int b[n], c[n], t[n], x, j, N=0, L=0, m=-1;
    for(j=n; --j>0;)
        b[j]=c[j]=0;
    b[0]=c[0]=1;
    for(; N<n; ++N){
        x = s[N];
        for(j=L; j>0; --j)
            x ^= c[j]&s[N-j];
        if (x!=0){
            for(j=n; --j>=0;)
                t[j]=c[j];
            for(j=n-N+m; --j>=0;)
                c[N-m+j] ^= b[j];
            if(L+L<=N){
                L=N+1-L;
                m=N;
                for(j=n; --j>0;)
                    b[j]=t[j];
            }
        }
    }
    printf("s =");
    for(j=0; j<n; j++)
        printf(" %d",s[j]);
    printf("\nc =");
    for(j=0; j<n; j++)
        printf(" %d",c[j]);
    printf("\nL = %d\n",L);
    return 0;
}