alg_c.c


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

#define MAX(A, B) (((A) > (B)) ? (A) : (B))

int main(int argv, char **argc) {
    if (argv < 3) {
        assert(argv > 0);
        printf("Usage: %s [n] [t]\n", argc[0]);
        return -1;
    }

    long n = atoi(argc[1]),
         t = atoi(argc[2]),
         s = n - t;

    assert(1 < t && t < n);

    char *a = calloc(n, sizeof(*a)),
         *w = calloc(n + 1, sizeof(*a));

C1_initialize:
    for (size_t j = 0; j < s; j++)
        a[j] = 0;
    for (size_t j = s; j < n; j++)
        a[j] = 1;
    for (size_t j = 0; j <= n; j++)
        w[j] = 1;
    size_t r = (s > 0) ? s : t;

C2_visit:
    for (size_t k = n; k --> 0;)
        printf("%lu", a[k]);
    printf("\n");

C3_find_j_and_branch:
    size_t j = r;
    while (w[j] == 0) {
        w[j] = 1;
        j = j + 1;
    }
    if (j == n) return 0;
    w[j] = 0;
    if (j % 2 == 1 && a[j] != 0) goto C4_move_right_one;
    if (j % 2 == 0 && a[j] != 0) goto C5_move_right_two;
    if (j % 2 == 0 && a[j] == 0) goto C6_move_left_one;
    if (j % 2 == 1 && a[j] == 0) goto C7_move_left_two;

C4_move_right_one:
    a[j - 1] = 1;
    a[j] = 0;
    if (r == j && j > 1)    r = j - 1;
    else if (r == j - 1)    r = j;
    goto C2_visit;

C5_move_right_two:
    if (a[j - 2] != 0) goto C4_move_right_one;
    a[j - 2] = 1;
    a[j] = 0;
    if (r == j)             r = MAX(j - 2, 1);
    else if (r == j - 2)    r = j - 1;
    goto C2_visit;

C6_move_left_one:
    a[j] = 1;
    a[j - 1] = 0;
    if (r == j && j > 1)    r = j - 1;
    else if (r == j - 1)    r = j;
    goto C2_visit;

C7_move_left_two:
    if (a[j - 1] != 0) goto C6_move_left_one;
    a[j] = 1;
    a[j - 2] = 0;
    if (r == j - 2)         r = j;
    else if (r == j - 1)    r = j - 2;
    goto C2_visit;
}