poj 3083 Children of the Candy Corn 解题报告-- DFS BFS

题目大意：给出一个迷宫，#表示墙，S表示起点，E表示终点。求从S到E的优先靠左边的墙走、优先靠右边的墙走和S到E的最短路径。

思路：考虑向左向右用DFS，最短路径用BFS。注意几点，一是尽量不用递归，开始用的递归，BFS会栈溢出，改用队列实现后没问题，而且其实逻辑上反而更统一，这里DFS还好，递归没有问题，大概是因为有向左向右的规则，并不是一味地遍历所有状态；再一个就是BFS实在是状态太多，必须限制，可以标记会走的点，不让这些点重复地进入队列。

当然，这个代码明显有很多可以修改的地方，在写的过程中由于偷懒不影响结果的就没改了。主要是练手而已，重在细心。

代码：

#include<stdio.h>#include <stdlib.h>#include "queue"using namespace std;#define LEN 42//最外层不通typedef struct {int x,y;int dx,dy;int layer;} NODE;char maze[LEN][LEN];int w,h;int ln,rn,sn;void ini_maze(int *sx , int *sy){int i,j;for(i=0;i < LEN ; i++)for(j=0; j < LEN ; j++)maze[i][j]='#';for(i=1; i<=h; i++){getchar();for(j=1; j<=w; j++){scanf("%c",&maze[j][i]);if('S' == maze[j][i]){*sx = j;*sy = i;}}}ln = 1; rn =1; sn = 5001;}void find_sway(int x, int y, int dx, int dy , int layer){int lres = -1, rres = -1, mres = -1;NODE nod,td;queue<NODE> qlist;x += dx;y += dy;while(maze[x][y] != 'E'){if( maze[x+dy][y-dx] != '#')//向左{nod.dx = dy;nod.dy = -dx;nod.x = x;nod.y = y;nod.layer = layer+1;qlist.push(nod);if(maze[x+dy][y-dx] != 'E')maze[x+dy][y-dx] = '#';}if( maze[x-dy][y+dx] != '#')//向右{nod.dx = -dy;nod.dy = dx;nod.x = x;nod.y = y;nod.layer = layer+1;qlist.push(nod);if(maze[x-dy][y+dx] != 'E')maze[x-dy][y+dx] = '#';}if( maze[x+dx][y+dy] != '#')//向前{nod.dx = dx;nod.dy = dy;nod.x = x;nod.y = y;nod.layer = layer+1;qlist.push(nod);if(maze[x+dx][y+dy] != 'E')maze[x+dx][y+dy] = '#';}td = qlist.front();x = td.x + td.dx;y = td.y + td.dy;dx = td.dx;dy = td.dy;layer = td.layer;qlist.pop();}sn = layer;}int find_lway(int x, int y, int dx, int dy , int layer){int lres = -1, rres = -1, mres = -1;ln++;x += dx;y += dy;if( maze[x][y] == 'E'){return layer;}if( maze[x+dy][y-dx] != '#')//向左{lres = find_lway(x,y,dy,-dx,layer+1);if(lres == -1)ln++;}if(lres == -1){if( maze[x+dx][y+dy] != '#')//向前{mres = find_lway(x,y,dx,dy,layer+1);if(mres == -1)ln++;}if(mres == -1){if( maze[x-dy][y+dx] != '#')//向右{rres = find_lway(x,y,-dy,dx,layer+1);if(rres == -1)ln++;}if(rres == -1){return -1;}}}return 0;}int find_rway(int x, int y, int dx, int dy , int layer){int lres = -1, rres = -1, mres = -1;rn++;x += dx;y += dy;if( maze[x][y] == 'E'){return layer;}if( maze[x-dy][y+dx] != '#')//right{rres = find_rway(x,y,-dy,dx,layer+1);if(rres == -1)rn++;}if(rres == -1){if( maze[x+dx][y+dy] != '#')//向前{mres = find_rway(x,y,dx,dy,layer+1);if(mres == -1)rn++;}if(mres == -1){if( maze[x+dy][y-dx] != '#')//left{lres = find_rway(x,y,dy,-dx,layer+1);if(lres == -1)rn++;}if(lres == -1){return -1;}}}return 0;}int main(){int sx , sy,i,n;//freopen("in.txt","r",stdin);scanf("%d",&n);for(i=1; i<=n; i++){scanf("%d%d",&w,&h);ini_maze(&sx,&sy);if(1 == sx){find_lway(sx,sy,1,0,2);find_rway(sx,sy,1,0,2);find_sway(sx,sy,1,0,2);}if(1 == sy){find_lway(sx,sy,0,1,2);find_rway(sx,sy,0,1,2);find_sway(sx,sy,0,1,2);}if(w == sx){find_lway(sx,sy,-1,0,2);find_rway(sx,sy,-1,0,2);find_sway(sx,sy,-1,0,2);}if(h == sy){find_lway(sx,sy,0,-1,2);find_rway(sx,sy,0,-1,2);find_sway(sx,sy,0,-1,2);}printf("%d %d %d\n",ln,rn,sn);}system("pause");return 0;}