POJ 3074 suduku

来源：互联网发布：中北大学软件工程学院编辑：程序博客网时间：2024/05/18 00:54

DLX精确覆盖的应用: sudouku问题求解

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;char sudoku[100];const int N = 9;const int TN = N*N*N+10;const int TM = N*N*4+10;const int TV = TN*TM;struct DLX{    int n,m,size;    int U[TV],D[TV],R[TV],L[TV],Row[TV],Col[TV];    int H[TN],S[TM];    int ansd, ans[TN];    void init(int _n,int _m){        n = _n;        m = _m;        for(int i = 0;i <= m;i++){            S[i] = 0;             U[i] = D[i] = i;            L[i] = i-1;            R[i] = i+1;}        R[m] = 0; L[0] = m;        size = m;        for(int i = 1;i <= n;i++) H[i] = -1;     }    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){        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 resume(int c){        L[R[c]] = R[L[c]] = c;        for(int i = U[c];i != c;i = U[i])            for(int j = R[i];j != i;j = R[j])                ++S[Col[U[D[j]]=D[U[j]]=j]];    }    bool Dance(int d){        if(R[0] == 0){                        for(int i=0;i<d;++i) sudoku[(ans[i]-1)/N] = (ans[i]-1)%9+'1';            puts(sudoku);            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(Dance(d+1)) return true;            for(int j = L[i]; j != i;j = L[j]) resume(Col[j]);        }        resume(c);        return false;    }}dlx;

void place(int& r,int& c1,int& c2,int& c3,int& c4,int i,int j,int k){r = (i*N+j)*N+k;c1 = i*N+j+1;c2 = N*N+N*i+k;c3 = N*N*2+N*j+k;c4 = N*N*3+(i/3*3+j/3)*N+k; }int main(){while(scanf("%s",sudoku),sudoku[0]!='e'){dlx.init(N*N*N,N*N*4);for(int i=0;i<N;++i)for(int j=0;j<N;++j)for(int k=1;k<=N;++k){if(sudoku[i*N+j]=='.'||sudoku[i*N+j]==k+'0'){int r,c1,c2,c3,c4;place(r,c1,c2,c3,c4,i,j,k);dlx.Link(r,c1);dlx.Link(r,c2);dlx.Link(r,c3);dlx.Link(r,c4);}}dlx.Dance(0);}return 0;}

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