bzoj1085 [SCOI2005]骑士精神

Posted 2020-09-14

　　IDA*裸题，其实就是dfs加个最优性减枝。

#include<cstdio>
inline void swap(int &x,int &y){int t=x; x=y; y=t;}
const int map[5][5]={
    1,1,1,1,1,
    0,1,1,1,1,
    0,0,2,1,1,
    0,0,0,0,1,
    0,0,0,0,0
};
const int xx[8]={1,1,-1,-1,2,2,-2,-2};
const int yy[8]={2,-2,2,-2,1,-1,1,-1};
int yes=0,a[5][5],b[5][5];
void search(int tot,int to,int x,int y,int num){
    if(tot==to){if(!num) yes=1; return;}
    for(int i=0;i<8;i+=1){
        if(yes) return;
        int tox=x+xx[i],toy=y+yy[i]; int t=num;
        if(tox<0 || tox>4 || toy<0 || toy>4) continue;
        if(a[x][y]==map[x][y]) num+=1;
        if(a[tox][toy]==map[tox][toy]) num+=1;
        swap(a[x][y],a[tox][toy]);
        if(a[x][y]==map[x][y]) num-=1;
        if(a[tox][toy]==map[tox][toy]) num-=1;
        if(num+tot<=to) search(tot+1,to,tox,toy,num);
        swap(a[x][y],a[tox][toy]); num=t;
    }
}
int main(){
    int T,x,y;
    for(scanf("%d",&T);T;T-=1){
        for(int i=0;i<5;i+=1)
            for(int j=0;j<5;j+=1){
                char c; while(c=getchar(),(c<‘0‘ || c>‘1‘) && c!=‘*‘);
                if(c!=‘*‘)a[i][j]=c-‘0‘; else {a[i][j]=2; x=i;y=j;}
            }
        int num=0;
        for(int i=0;i<5;i+=1)
            for(int j=0;j<5;j+=1)
                if(a[i][j]!=map[i][j]) num++;
        for(int i=num-1;i<=15;i+=1){
            search(0,i,x,y,num);
            if(yes){printf("%d\n",i); break;}
        }
        yes?yes=0:printf("-1\n");
    }
    return 0;
}