poj1915 BFS

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/** * poj1915 BFS * 乍一看以为是DP，想了半天也没有想出一个特别好的dp方案来，果然还是走BFS吧 * 做法比较简单粗暴了，代码也很粗暴，就是宽搜，从最初始点开始，8种方向只要能走就走一步，只要这个点还没有走过，就将其作为新的出现的点记录下来 * 依照步数从小往大升序地遍历，得到的一定是最小值 */#include <cstdio>#include <cstring>const int MAX_NUM = 301;struct point{    int x;    int y;    int step;} p[MAX_NUM*MAX_NUM];bool flag[MAX_NUM][MAX_NUM];int l;int father,child;int xstart,xend,ystart,yend;void bfs(){    father = 0;    child = 1;    p[0].x = xstart;    p[0].y = ystart;    p[0].step = 0;    flag[xstart][ystart] = true;    int x,y,step;    if(xstart == xend && ystart == yend){        printf("0\n");        return;    }    while(1){        x = p[father].x;        y = p[father].y;        step = p[father].step;        //x-2 y-1        if(x>=2 && y>=1){            if(!flag[x-2][y-1]){                flag[x-2][y-1] = true;                p[child].x = x-2;                p[child].y = y-1;                p[child].step = step+1;                if(p[child].x == xend && p[child].y == yend){                    break;                }                ++child;            }        }        //x-2 y+1        if(x>=2 && y<l-1){            if(!flag[x-2][y+1]){                flag[x-2][y+1] = true;                p[child].x = x-2;                p[child].y = y+1;                p[child].step = step+1;                if(p[child].x == xend && p[child].y == yend){                    break;                }                ++child;            }        }        //x-1 y+2        if(x>=1 && y<l-2){            if(!flag[x-1][y+2]){                flag[x-1][y+2] = true;                p[child].x = x-1;                p[child].y = y+2;                p[child].step = step+1;                if(p[child].x == xend && p[child].y == yend){                    break;                }                ++child;            }        }        //x-1 y-2        if(x>=1 && y>=2){            if(!flag[x-1][y-2]){                flag[x-1][y-2] = true;                p[child].x = x-1;                p[child].y = y-2;                p[child].step = step+1;                if(p[child].x == xend && p[child].y == yend){                    break;                }                ++child;            }        }        //x+1 y-2        if(x<l-1 && y>=2){            if(!flag[x+1][y-2]){                flag[x+1][y-2] = true;                p[child].x = x+1;                p[child].y = y-2;                p[child].step = step+1;                if(p[child].x == xend && p[child].y == yend){                    break;                }                ++child;            }        }        //x+1 y+2        if(x<l-1 && y<l-2){            if(!flag[x+1][y+2]){                flag[x+1][y+2] = true;                p[child].x = x+1;                p[child].y = y+2;                p[child].step = step+1;                if(p[child].x == xend && p[child].y == yend){                    break;                }                ++child;            }        }        //x+2 y-1        if(x<l-2 && y>=1){            if(!flag[x+2][y-1]){                flag[x+2][y-1] = true;                p[child].x = x+2;                p[child].y = y-1;                p[child].step = step+1;                if(p[child].x == xend && p[child].y == yend){                    break;                }                ++child;            }        }        //x+2 y+1        if(x<l-2 && y<l-1){            if(!flag[x+2][y+1]){                flag[x+2][y+1] = true;                p[child].x = x+2;                p[child].y = y+1;                p[child].step = step+1;                if(p[child].x == xend && p[child].y == yend){                    break;                }                ++child;            }        }        ++father;    }    printf("%d\n",p[child].step);}int main(){    int t;    scanf("%d",&t);    while(t--){        scanf("%d",&l);        scanf("%d%d%d%d",&xstart,&ystart,&xend,¥d);        for(int i=0;i<l;++i){            memset(flag[i],0,sizeof(flag[i]));        }        bfs();    }    return 0;}
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