TOJ简单版贪吃蛇(bfs)

简单版贪吃蛇  

Time Limit(Common/Java):1000MS/3000MS     Memory Limit:65536KByte
Total Submit: 22            Accepted: 13 Special Judge

Description

现在我们来简化蛇的身体，假设初始化的时候蛇的身体只有一个头而已（呵，当然是假设的），那么蛇去吃食物的时候就不必考虑碰到自己的身体了。
例：

5 5
.....
S....
###.#
E....
#####

那么从S到E最短的走法是EEESSWWW。说明：N（north），S（south），W（west），E（east）。如果吃不到食物就输出Can't eat it!
注意：路径是最短的走的。

Input

输入数据有多组，每组输入的第一行是两个正整数R，C，表示行和列，3=<R，C<=100，下面输入R行C列的矩阵。

输入保证合法。

Output

每行输出最短的走法。

Sample Input

5 5
.....
S....
###.#
E....
#####

Sample Output

EEESSWWW

Uploader

helihui

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <cmath>
const int INF = 0x7fffffff;

using namespace std;
const int maxn = 110;
char g[maxn][maxn];
int n, m;
int used[maxn][maxn];//保存从s到这点最小步数
string trace[maxn][maxn];//记录路径.

struct info {
    int x;
    int y;
    int time;
};
info start, endx;
queue<info> Q;

void init() {
    while(!Q.empty()) Q.pop();
    memset(g, '\0', sizeof(g));
}

void bfs() {
    Q.push(start);
    info tmp, in;
    while(!Q.empty()) {
        tmp = Q.front();
        Q.pop();
        if(tmp.x - 1 >= 1 && g[tmp.x-1][tmp.y] != '#'){// up
            if(tmp.time + 1 < used[tmp.x-1][tmp.y]) {
                used[tmp.x-1][tmp.y] = tmp.time + 1;
                trace[tmp.x-1][tmp.y] = trace[tmp.x][tmp.y] + 'N';
                in.x = tmp.x - 1;
                in.y = tmp.y;
                in.time = used[tmp.x-1][tmp.y];
                Q.push(in);
            }
        }
        if(tmp.x + 1 <= n && g[tmp.x+1][tmp.y] != '#') {//down
            if(tmp.time + 1 < used[tmp.x+1][tmp.y]) {
                used[tmp.x+1][tmp.y] = tmp.time + 1;
                trace[tmp.x+1][tmp.y] = trace[tmp.x][tmp.y] + 'S';
                in.x = tmp.x + 1;
                in.y = tmp.y;
                in.time = used[tmp.x+1][tmp.y];
                Q.push(in);
            }
        }
        if(tmp.y - 1 >= 1 && g[tmp.x][tmp.y-1] != '#') {//left
            if(tmp.time + 1 < used[tmp.x][tmp.y-1]) {
                used[tmp.x][tmp.y-1] = tmp.time + 1;
                trace[tmp.x][tmp.y-1] = trace[tmp.x][tmp.y] + 'W';
                in.x = tmp.x;
                in.y = tmp.y  - 1;
                in.time = used[tmp.x][tmp.y-1];
                Q.push(in);
            }
        }
        if(tmp.y + 1 <= m && g[tmp.x][tmp.y+1] != '#') {//right
            if(tmp.time + 1 < used[tmp.x][tmp.y+1] ) {
                used[tmp.x][tmp.y+1] = tmp.time + 1;
                trace[tmp.x][tmp.y+1] = trace[tmp.x][tmp.y] + 'E';
                in.x = tmp.x;
                in.y = tmp.y + 1;
                in.time = used[tmp.x][tmp.y+1];
                Q.push(in);
            }
        }
    }
   if(used[endx.x][endx.y] == INF) {
        printf("Can't eat it!\n");
   } else {
        cout << trace[endx.x][endx.y] << endl;
   }
}

int main()
{
    int i, j;
    while(scanf("%d%d", &n, &m) != EOF) {
        init();
        for(i = 1; i <= n; i++) {
            scanf("%s", g[i]+1);
        }
        for(i = 1; i <= n; i++) {
            for(j = 1; j <= m; j++) {
                if(g[i][j] == 'S') {
                    start.x = i;
                    start.y = j;
                    start.time = 0;
                    used[i][j] = 0;//开始步数.
                }
                if(g[i][j]=='E') {
                    endx.x = i;
                    endx.y = j;
                }
                if(g[i][j] != 'S')
                    used[i][j] = INF;//初始化每个值.
                trace[i][j].clear();
            }
        }
        bfs();
    }
    return 0;
}

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
const int N = 105;
//注释：这是宾哥的代码，感觉写的不错，以后A掉题目后也有借鉴别人的代码风格。
int n, m;
char map[N][N];
struct Point {
	int x, y;
	string steps;
};
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0}; // E, W, S, N
string ds[] = {"E", "W", "S", "N"};
bool ok(int x, int y) {
	return (x >= 0 && x < m && y >= 0 && y < n && map[x][y] != '#');
}
Point you;
string bfs() {
    queue<Point> Q;
	Q.push(you);
	Point cur, nex;
	while(!Q.empty()) {
		cur = Q.front(); Q.pop();
		for(int i = 0; i < 4; i++) {
			nex.x = cur.x + dx[i];
			nex.y = cur.y + dy[i];
			if(!ok(nex.x, nex.y)) continue;
			if(map[nex.x][nex.y] == 'E') {
				return cur.steps + ds[i];
			}
			nex.steps = cur.steps + ds[i];
			map[nex.x][nex.y] = '#';
			Q.push(nex);
		}
	}
	return "-1";
}
int main() {
	while(scanf("%d%d", &m, &n) != EOF) {
		for(int i = 0; i < m; i++) {
			scanf("%s", map[i]);
			for(int j = 0; j < n; j++) {
				if(map[i][j] == 'S') {
					you.x = i;
					you.y = j;
					map[i][j] = '#';
					you.steps = "";
				}
			}
		}
		string ans = bfs();
		if(ans == "-1")
			printf("Can't eat it!");
		else cout << ans;
		printf("\n");
	}
	return 0;
}