hdu 1010 Tempter of the Bone_奇偶剪枝+dfs

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题目链接： ~click here ~

奇偶剪枝解释：~click here~

#include <cstdio>#include <cstring>#include <iostream>#include <stdlib.h>using namespace std;char map[9][9];int dx[4]={0,0,-1,1};int dy[4]={-1,1,0,0};int n,m,t,sum;int sx,sy,ddx,ddy;bool dfs(int x,int y,int time){    int px,py;    if(x==ddx && y==ddy && time==t)    {        return true;//正确    }    else    {        if(abs(ddx-x)+abs(ddy-y)>t-time)return false;        for(int i=0;i<4;i++)        {            px=x+dx[i];            py=y+dy[i];            if(map[px][py]!='X' && time+1<=t)            {                map[px][py]='X';                if(dfs(px,py,time+1))return true;                map[px][py]='.';            }        }    }    return false;}int main(){    while(scanf("%d%d%d",&n,&m,&t),n || m || t)    {        memset(map,'X',sizeof(map));         sum=0;        getchar();        for(int i=1;i<=n;i++)        {            for(int j=1;j<=m;j++)            {                scanf("%c",&map[i][j]);                if(map[i][j]=='S')                {                    sx=i;                    sy=j;                }                if(map[i][j]=='D')                {                    ddx=i;                    ddy=j;                }                if(map[i][j]=='.')sum++;            }            getchar();        }        if(sum+1<t || (t+sx+sy+ddx+ddy)%2==1)printf("NO\n"); //奇偶性判别与可达性判别        else        {            map[sx][sy]='X';            if(dfs(sx,sy,0))printf("YES\n");            else printf("NO\n");        }    }    return 0;}

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