这题数据水,可以直接暴力DFS解决
然后学了下 dancing links 就试着解决这题
#include <iostream> #include <cstdio> #include <cstring> #include <vector> using namespace std; const int N = 9; const int MAXN = N*N*N + 10; const int MAXM = N*N*4 + 10; const int M = MAXN*4 + MAXM; char g[N][N]; struct DLX{ int n, m, size; int U[M], D[M], R[M], L[M], Row[M], Col[M]; int H[MAXN], S[MAXM]; int ansd, ans[MAXN]; 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){ for(int i = U[c]; i != c; i = U[i]) for(int j = L[i];j != i;j = L[j]) ++S[Col[U[D[j]] = D[U[j]]=j]]; L[R[c]] = R[L[c]] = c; } bool Dance(int d){ if(R[0] == 0){ for(int i = 0;i < d;i++)g[(ans[i]-1)/9/9][(ans[i]-1)/9%9] = (ans[i]-1)%9 + '1'; for(int i = 0 ; i < N; i++){ for(int j = 0; j < N; j++){ printf("%c",g[i][j]); } printf("\n"); } 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+i*N+k; c3 = N*N*2+j*N+k; c4 = N*N*3+((i/3)*3+(j/3))*N+k; } int main(){ int t; int r,c1,c2,c3,c4; scanf("%d",&t); while(t--){ dlx.init(N*N*N,N*N*4); for(int i = 0 ; i < N; i++){ scanf("%s",g[i]); for(int j = 0; j < N; j++){ for(int k = 1; k <= 9; k++){ if(g[i][j] == '0' || g[i][j] == '0'+k){ 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; }