【UVa】387 A Puzzling Problem

#include<cstdio>
#include<cstring>
#define MAXM 10
#define MAXN 100000
#define MAXL 110
#define INF 0x7FFFFFFF
struct node {
    int h, l;
    char s[MAXM][MAXM];
};
struct answer {
    int pos, h, l;
};
answer ans[MAXL];
node sq[MAXM];
bool vis[MAXL];
int L[MAXN], R[MAXN], U[MAXN], D[MAXN];
int H[MAXN], S[MAXN], C[MAXN], X[MAXN];
int size;
char a[MAXM][MAXM];
void Init(int m) {
    int i;
    memset(vis, false, sizeof(vis));
    for (i = 0; i <= m; i++) {
        L[i + 1] = i;
        R[i] = i + 1;
        U[i] = D[i] = i;
        S[i] = 0;
    }
    R[m] = 0;
    size = m + 1;
}
void Link(int r, int c) {
    U[size] = c;
    D[size] = D[c];
    U[D[c]] = size;
    D[c] = size;
    if (H[r] < 0)
        H[r] = L[size] = R[size] = size;
    else {
        L[size] = H[r];
        R[size] = R[H[r]];
        L[R[H[r]]] = size;
        R[H[r]] = size;
    }
    S[c]++;
    X[size] = r;
    C[size++] = c;
}
void Remove(int c) {
    int i, j;
    L[R[c]] = L[c];
    R[L[c]] = R[c];
    for (i = D[c]; i != c; i = D[i]) {
        for (j = R[i]; j != i; j = R[j]) {
            U[D[j]] = U[j];
            D[U[j]] = D[j];
            S[C[j]]--;
        }
    }
}
void Resume(int c) {
    int i, j;
    L[R[c]] = R[L[c]] = c;
    for (i = D[c]; i != c; i = D[i]) {
        for (j = R[i]; j != i; j = R[j]) {
            U[D[j]] = D[U[j]] = j;
            S[C[j]]++;
        }
    }
}
bool Dance() {
    if (R[0] == 0)
        return true;
    int i, j, temp, c;
    for (temp = INF,i = R[0]; i; i = R[i]) {
        if (temp > S[i]) {
            temp = S[i];
            c = i;
        }
    }
    Remove(c);
    for (i = D[c]; i != c; i = D[i]) {
        vis[X[i]] = true;
        for (j = R[i]; j != i; j = R[j])
            Remove(C[j]);
        if (Dance())
            return true;
        for (j = L[i]; j != i; j = L[j])
            Resume(C[j]);
        vis[X[i]] = false;
    }
    Resume(c);
    return false;
}
void Build(int n) {
    int i, j, k, t, p, r;
    for (i = r = 0; i < n; i++) {
        for (j = 0; j <= 4 - sq[i].h; j++) {
            for (k = 0; k <= 4 - sq[i].l; k++) {
                H[++r] = -1;
                Link(r, 16 + i + 1);
                ans[r].pos = i;
                ans[r].h = j;
                ans[r].l = k;
                for (t = 0; t < sq[i].h; t++) {
                    for (p = 0; p < sq[i].l; p++) {
                        if (sq[i].s[t][p] != '0')
                            Link(r, 4 * (j + t) + k + p + 1);
                    }
                }
            }
        }
    }
}
int main() {
    int n, i, j, k;
    bool flag = true;
    while (scanf("%d", &n), n) {
        if (flag)
            flag = false;
        else
            putchar('\n');
        Init(16 + n);
        for (i = 0; i < n; i++) {
            scanf("%d%d", &sq[i].h, &sq[i].l);
            for (j = 0; j < sq[i].h; j++) {
                for (k = 0; k < sq[i].l; k++)
                    scanf(" %c", &sq[i].s[j][k]);
            }
        }
        Build(n);
        if (Dance()) {
            for (i = 1; i < MAXL; i++) {
                if (vis[i]) {
                    for (j = 0; j < sq[ans[i].pos].h; j++) {
                        for (k = 0; k < sq[ans[i].pos].l; k++) {
                            if (sq[ans[i].pos].s[j][k] != '0')
                                a[j + ans[i].h][k + ans[i].l] = '1'
                                        + ans[i].pos;
                        }
                    }
                }
            }
            for (i = 0; i < 4; i++) {
                for (j = 0; j < 4; j++)
                    putchar(a[i][j]);
                putchar('\n');
            }
        } else
            puts("No solution possible");
    }
    return 0;
}