POJ 3074 Sudoku 舞蹈链

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <queue>
#include <stack>
#include <cstdlib>
#include <cmath>
#include <set>
#include <map>
#include <vector>
#include <cstring>

#define INF 100000000
using namespace std;
#define maxn 10000
#define maxnode 270000

struct DLX{
	int n,sz;
	int S[maxn];
	int row[maxnode],col[maxnode];
	int L[maxnode],R[maxnode],U[maxnode],D[maxnode];
	int ansd,ans[100];
	void init(int q) {
        n = q;
        for(int i = 0; i <= n; i++) {
            U[i] = i; D[i] = i; L[i] = i - 1; R[i] = i + 1;
        }
        R[n] = 0; L[0] = n;
        sz = n+1;
        memset(S, 0, sizeof(S));
    }  

	 void addRow(int r, vector<int> columns) {
        int first = sz;
        for(int i = 0; i < columns.size(); i++) {
            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) {
        for(int i = U[c]; i != c; i = U[i])
            for(int j = L[i]; j != i; j = L[j]) {
                ++S[col[j]];
                U[D[j]] = j;
                D[U[j]] = j;
            }
        L[R[c]] = c;
        R[L[c]] = c;
    }
	bool dfs(int d){
		if(R[0] == 0){
			ansd = d;
			return true;
		}
		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;
	}
};
char puzzle[11][11];
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*81+b*9+c+1;
}
void decode(int code,int &a,int &b,int &c){
	code --;
	c = code%9;
	code /= 9;
	b = code%9;
	code /= 9;
	a = code;
}
char ch[100];
int len[100];
DLX solver;
int main(){
	while(scanf("%s",ch)!=EOF){
		if(strcmp(ch,"end")== 0) break;
		solver.init(324);
		for(int i = 0;ch[i];i++){
			puzzle[i/9][i%9] = ch[i];

		}
		for(int r = 0;r < 9;r++){
			for(int c = 0;c < 9;c++){
				for(int k = 0;k < 9;k++){
					if(puzzle[r][c] == '.' || puzzle[r][c] == k + '1'){
						vector<int> vec;
						vec.push_back(encode(SLOT,r,c));
						vec.push_back(encode(ROW,r,k));
						vec.push_back(encode(COL,c,k));
						vec.push_back(encode(SUB,((r/3)*3+c/3),k));
						solver.addRow(encode(r,c,k),vec);
					}
				}
			}
		}

		solver.dfs(0);
		for(int i = 0;i < solver.ansd;i++){
			int r,c,v;
			decode(solver.ans[i],r,c,v);
			puzzle[r][c] = v;
		}

		for(int i = 0;i < 81;i++){
			printf("%c",puzzle[i/9][i%9]+'1');
		}cout << endl;

	}
	return 0;
}