int pattern[] = { 1, 2, 3, 1 };  /* I use int instead of char, simpler */
const int n = sizeof(pattern) / 4;
int D[n];
int f[n];

int j = n;
int t = n + 1;

for (int k = 1; k <= n; k++){
    D[k-1] = 2 * n - k;
}

while (j > 0) {
    f[j-1] = t;
    while (t <= n) {
        if (pattern[j-1] != pattern[t-1]) {
            D[t-1] = min(D[t-1], n - j);
            t = f[t-1];
        }
        else {
            break;
        }
    }
    t = t - 1;
    j = j - 1;
}

int f1[n];
int q = t;
t = n + 1 - q;
int q1 = 1;
int j1 = 1;
int t1 = 0;


while (j1 <= t) {
    f1[j1 - 1] = t1;
    while (t1 >= 1) {
        if (pattern[j1 - 1] != pattern[t1 - 1]) {
            t1 = f1[t1 - 1];
        }
        else {
            break;
        }
    }
    t1 = t1 + 1;
    j1 = j1 + 1;
}
while (q < n) {
    for (int k = q1; k <= q; k++) {
        D[k - 1] = min(D[k - 1], n + q - k);
    }
    q1 = q + 1;
    q = q + t - f1[t - 1];
    t = f1[t - 1];
}

for (int i = 0; i < n; i++)
{
    cout << D[i] << " ";
}