【HDOJ】3909 Sudoku

DLX的应用，基本题，注意maxnode开大点儿。

/* 3909 */
#include <iostream>
#include <string>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <deque>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <climits>
#include <cctype>
#include <cassert>
#include <functional>
#include <iterator>
#include <iomanip>
using namespace std;
//#pragma comment(linker,"/STACK:102400000,1024000")

#define sti                set<int>
#define stpii            set<pair<int, int> >
#define mpii            map<int,int>
#define vi                vector<int>
#define pii                pair<int,int>
#define vpii            vector<pair<int,int> >
#define rep(i, a, n)     for (int i=a;i<n;++i)
#define per(i, a, n)     for (int i=n-1;i>=a;--i)
#define clr                clear
#define pb                 push_back
#define mp                 make_pair
#define fir                first
#define sec                second
#define all(x)             (x).begin(),(x).end()
#define SZ(x)             ((int)(x).size())
#define lson            l, mid, rt<<1
#define rson            mid+1, r, rt<<1|1

typedef struct DLX {
    static const int maxc = 4*16*16+5;
    static const int maxr = 16*16*16+5;
    static const int maxnode = 16*16*16*5+5;
    
    int n, sz;
    int S[maxc];
    
    int row[maxnode], col[maxnode];
    int L[maxnode], R[maxnode], U[maxnode], D[maxnode];
    
    int ansd, cnt, ans[maxr], ans_[maxr];
    
    void init(int n_) {
        cnt = 0;
        n = n_;
        
        rep(i, 0, n+1) {
            L[i] = i-1;
            R[i] = i+1;
            U[i] = i;
            D[i] = i;
        }
        
        L[0] = n;
        R[n] = 0;
        
        sz = n+1;
        memset(S, 0, sizeof(S));
    }
    
    void addRow(int r, vi columns) {
        int first = sz;
        int size = SZ(columns);
        
        rep(i, 0, size) {
            int c = columns[i];
            
            L[sz] = sz-1;
            R[sz] = sz+1;
            
            D[sz] = c;
            U[sz] = U[c];
            D[U[c]] = sz;
            U[c] = sz;
            
            row[sz] = r;
            col[sz] = c;
            
            ++S[c];
            ++sz;
        }
        
        R[sz - 1] = first;
        L[first] = sz - 1;
    }
    
    void remove(int c) {
        L[R[c]] = L[c];
        R[L[c]] = R[c];
        for (int i=D[c]; i!=c; i=D[i]) {
            for (int j=R[i]; j!=i; j=R[j]) {
                U[D[j]] = U[j];
                D[U[j]] = D[j];
                --S[col[j]];
            }
        }
    }
    
    void restore(int c) {
        L[R[c]] = c;
        R[L[c]] = c;
        for (int i=D[c]; i!=c; i=D[i]) {
            for (int j=R[i]; j!=i; j=R[j]) {
                U[D[j]] = j;
                D[U[j]] = j;
                ++S[col[j]];
            }
        }
    }
    
    bool dfs(int d) {
        if (R[0] == 0) {
            ansd = d;
            ++cnt;
            rep(i, 0, ansd)
                ans_[i] = ans[i];
            return cnt>1;
        }
        
        int c = R[0];
        for (int i=R[0]; i!=0; i=R[i]) {
            if (S[i] < S[c])
                c = i;
        }
        
        remove(c);
        for (int i=D[c]; i!=c; i=D[i]) {
            ans[d] = row[i];
            for (int j=R[i]; j!=i; j=R[j]) {
                remove(col[j]);
            }
            if (dfs(d + 1))    return true;
            for (int j=L[i]; j!=i; j=L[j]) {
                restore(col[j]);
            }
        }
        restore(c);
        
        return false;
    }
    
    void solve(vi& v) {
        
        dfs(0);
        
        if (cnt == 1) {
            v.clr();
            rep(i, 0, ansd)
                v.pb(ans_[i]);
        }
    }
    
} DLX;

DLX solver;
int n, n2, n2n2;
const int maxl = 20;
char M[maxl][maxl], M_[maxl][maxl];
const int SLOT     = 0;
const int ROW      = 1;
const int COL    = 2;
const int SUB    = 3;

int encode(int a, int b, int c) {
    return a*n2n2 + b*n2 + c + 1;
}

void decode(int code, int& a, int& b, int& c) {
    --code;
    c = code % n2;
    code /= n2;
    b = code % n2;
    code /= n2;
    a = code;
}

int getVal(char c) {
    if (c>='0' && c<='9')    return c-'1';
    return c-'A'+9;
}

int getChar(int val) {
    if (val < 9)    return val+'1';
    return val-9+'A';
}

void init() {
    n2 = n * n;
    n2n2 = n2 * n2;
}

void solve(vi& ans) {
    solver.init(4 * n2n2);
        
    rep(r, 0, n2) {
        rep(c, 0, n2) {
            rep(v, 0, n2) {
                if (M[r][c]=='.' || v==getVal(M[r][c])) {
                    vi columns;
                    columns.pb(encode(SLOT, r, c));
                    columns.pb(encode(ROW, r, v));
                    columns.pb(encode(COL, c, v));
                    columns.pb(encode(SUB, r/n*n+c/n, v));
                    solver.addRow(encode(r, c, v), columns);
                }
            }
        }
    }
    
    solver.solve(ans);
}

int main() {
    ios::sync_with_stdio(false);
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif
    
    vi ans, tmp;
    
    while (scanf("%d", &n) != EOF) {
        init();
        rep(i, 0, n2)
            scanf("%s", M[i]);        
        
        solve(ans);
        
        if (solver.cnt == 0) {
            puts("No Solution");
            continue;
        } else if (solver.cnt > 1) {
            puts("Multiple Solutions");
            continue;
        }
        
        // check if is minimal
        bool flag = true;
        
        rep(r, 0, n2) {
            rep(c, 0, n2) {
                if (M[r][c] != '.') {
                    char ch = M[r][c];
                    M[r][c] = '.';
                    solve(tmp);
                    M[r][c] = ch;
                    if (solver.cnt <= 1) {
                        flag = false;
                        goto _output;
                    }
                }
            }
        }
        
        _output:
        if (flag) {        
            int sz = SZ(ans);
            rep(i, 0, sz) {
                int r, c, v;
                decode(ans[i], r, c, v);
                char ch = getChar(v);
                M[r][c] = ch;
            }
            
            rep(i, 0, n2)
                puts(M[i]);
        } else {
            puts("Not Minimal");
        }
    }
    
    #ifndef ONLINE_JUDGE
        printf("time = %d.
", (int)clock());
    #endif
    
    return 0;
}