【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 = **+;
     static const int maxr = **+;
     static const int maxnode = ***+;

     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 = ;
         n = n_;

         rep(i, , n+) {
             L[i] = i-;
             R[i] = i+;
             U[i] = i;
             D[i] = i;
         }

         L[] = n;
         R[n] = ;

         sz = n+;
         memset(S, , sizeof(S));
     }

     void addRow(int r, vi columns) {
         int first = sz;
         int size = SZ(columns);

         rep(i, , size) {
             int c = columns[i];

             L[sz] = sz-;
             R[sz] = sz+;

             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 - ] = first;
         L[first] = sz - ;
     }

     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[] == ) {
             ansd = d;
             ++cnt;
             rep(i, , ansd)
                 ans_[i] = ans[i];
             return cnt>;
         }

         int c = R[];
         for (int i=R[]; i!=; 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 + ))    return true;
             for (int j=L[i]; j!=i; j=L[j]) {
                 restore(col[j]);
             }
         }
         restore(c);

         return false;
     }

     void solve(vi& v) {

         dfs();

         if (cnt == ) {
             v.clr();
             rep(i, , ansd)
                 v.pb(ans_[i]);
         }
     }

 } DLX;

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

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

 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>='' && c<='')    return c-'';
     return c-'A'+;
 }

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

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

 void solve(vi& ans) {
     solver.init( * n2n2);

     rep(r, , n2) {
         rep(c, , n2) {
             rep(v, , 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, , n2)
             scanf("%s", M[i]);        

         solve(ans);

         if (solver.cnt == ) {
             puts("No Solution");
             continue;
         } else if (solver.cnt > ) {
             puts("Multiple Solutions");
             continue;
         }

         // check if is minimal
         bool flag = true;

         rep(r, , n2) {
             rep(c, , n2) {
                 if (M[r][c] != '.') {
                     char ch = M[r][c];
                     M[r][c] = '.';
                     solve(tmp);
                     M[r][c] = ch;
                     if (solver.cnt <= ) {
                         flag = false;
                         goto _output;
                     }
                 }
             }
         }

         _output:
         if (flag) {
             int sz = SZ(ans);
             rep(i, , sz) {
                 int r, c, v;
                 decode(ans[i], r, c, v);
                 char ch = getChar(v);
                 M[r][c] = ch;
             }

             rep(i, , n2)
                 puts(M[i]);
         } else {
             puts("Not Minimal");
         }
     }

     #ifndef ONLINE_JUDGE
         printf("time = %d.\n", (int)clock());
     #endif

     return ;
 }