zoj 3209.Treasure Map（DLX精确覆盖）

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <vector>
using namespace std;

#define FOR(i,A,s)  for(int i = A[s]; i != s; i = A[i])
#define exp 1e-8

const int MAX = 510000;
int n, m, k, t, len;

struct DLX {
    int n, Size;//Size为尾指针，真正大小
    int row[MAX], col[MAX];//记录每个点的行列
    int U[MAX], D[MAX], R[MAX], L[MAX]; //4个链表
    int S[MAX],H[MAX];//每列1的个数
    int ncnt, ans[MAX];
    void init (int n) {
        this->n = n;
        ncnt = MAX;
        //增加n+1个辅助链表，从0到n
        for (int i = 0; i <= n; i++)
            U[i] = D[i] = i, L[i] = i - 1, R[i] = i + 1,S[i]=0;
        R[n] = 0, L[0] = n; //头尾相接
        Size = n + 1;
        memset (H, -1, sizeof H);
    }
    //单点添加
    void Link (int r, int c)
    {
        ++S[col[++Size] = c];
        row[Size] = r;
        D[Size] = D[c];
        U[D[c]] = Size;
        U[Size] = c;
        D[c] = Size;
        if (H[r] < 0) H[r] = L[Size] = R[Size] = Size;
        else
        {
            R[Size] = R[H[r]];
            L[R[H[r]]] = Size;
            L[Size] = H[r];
            R[H[r]] = Size;
        }
    }
    void Remove (int c) {
        //精确覆盖
        L[R[c]] = L[c], R[L[c]] = R[c];
        FOR (i, D, c)
        FOR (j, R, i)
        U[D[j]] = U[j], D[U[j]] = D[j], --S[col[j]];
//        //重复覆盖
//        for (int i = D[c]; i != c; i = D[i])
//            L[R[i]] = L[i], R[L[i]] = R[i];
    }
    void Restore (int c) {
        FOR (i, U, c)
        FOR (j, L, i)
        ++S[col[j]], U[D[j]] = j, D[U[j]] = j;
        L[R[c]] = c, R[L[c]] = c;
        //重复覆盖
//        for (int i = U[c]; i != c; i = U[i])
//            L[R[i]] = R[L[i]] = i;
    }
    bool v[MAX];
    int ff() {
        int ret = 0;
        for (int c = R[0]; c != 0; c = R[c]) v[c] = true;
        for (int c = R[0]; c != 0; c = R[c])
            if (v[c])
            {
                ret++;
                v[c] = false;
                for (int i = D[c]; i != c; i = D[i])
                    for (int j = R[i]; j != i; j = R[j])
                        v[col[j]] = false;
            }
        return ret;
    }
    bool dfs (int d) {
        if (d >= ncnt) return 0;
        //if (d + ff() > k) return 0;//重复覆盖
        if (R[0] == 0) {
            ncnt = min (ncnt, d);
            return 1;
        }
        int c = R[0];
        for (int i = R[0]; i != 0; i = R[i])
            if (S[i] < S[c])
                c = i;
        Remove (c);//精确覆盖
        FOR (i, D, c) {
            //Remove (i);//重复覆盖
            ans[d] = row[i];
            FOR (j, R, i) Remove (col[j]);//精确覆盖
            //FOR (j, R, i) Remove (j);//重复覆盖
            //if (dfs (d + 1) ) return 1;
            dfs (d + 1);
            FOR (j, L, i) Restore (col[j]);//精确覆盖
            //FOR (j, L, i) Restore (j);//重复覆盖
            //Restore (i);//重复覆盖
        }
        Restore (c);//精确覆盖
        return 0;
    }
    bool solve (vector<int> &v) {
        v.clear();
        if (!dfs (0) ) return 0;
        for (int i = 0; i < ncnt; i++) v.push_back (ans[i]);
        return 1;
    }
} Dance;
int columns[31][31 * 31];
int main() {
    scanf ("%d", &t);
    while (t--) {
        memset (columns, 0, sizeof columns);
        scanf ("%d %d %d", &n, &m, &k);
        len = n * m;
        Dance.init (len);
        int x,y,xx,yy;
        for (int p = 1; p <= k; p++) {
            scanf ("%d %d %d %d", &x, &y, &xx, &yy);
            for (int i = x+1; i <= xx; i++)
                for (int j = y+1; j <= yy; j++)
                    Dance.Link (p, j + (i-1)*m);
        }
        Dance.dfs (0);
        printf ("%d\n", Dance.ncnt == MAX ? -1 : Dance.ncnt);
    }
    return 0;
}