poj3009

简单题

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

#define maxn 25

struct Point
{
    int x, y;
} s, e;

bool map[maxn][maxn];
int n, m, ans;
bool found;
int dir[4][2] =
{
{ 0, 1 },
{ 1, 0 },
{ 0, -1 },
{ -1, 0 } };

void input()
{
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
        {
            int a;
            scanf("%d", &a);
            if (a == 1)
                map[i][j] = false;
            else
                map[i][j] = true;
            if (a == 2)
            {
                s.x = i;
                s.y = j;
            }
            if (a == 3)
            {
                e.x = i;
                e.y = j;
            }
        }
}

int fail(Point &a)
{
    if (a.x < 0 || a.y < 0 || a.x >= n || a.y >= m)
        return -1;
    if (!map[a.x][a.y])
        return 1;
    return 0;
}

void dfs(Point &a, int step)
{
    if (step >= 10)
        return;
    Point b;
    for (int i = 0; i < 4; i++)
    {
        b.x = a.x + dir[i][0];
        b.y = a.y + dir[i][1];
        if (fail(b))
            continue;
        int x;
        while (!(x = fail(b)))
        {
            if (b.x == e.x && b.y == e.y)
            {
                found = true;
                ans = min(ans, step + 1);
                return;
            }
            b.x += dir[i][0];
            b.y += dir[i][1];
        }
        if (x == -1)
            continue;
        map[b.x][b.y] = true;
        b.x -= dir[i][0];
        b.y -= dir[i][1];
        dfs(b, step + 1);
        b.x += dir[i][0];
        b.y += dir[i][1];
        map[b.x][b.y] = false;
    }
}

int main()
{
    //freopen("t.txt", "r", stdin);
    while (scanf("%d%d", &m, &n), m | n)
    {
        input();
        found = false;
        ans = 20;
        dfs(s, 0);
        if (found)
            printf("%d\n", ans);
        else
            printf("%d\n", -1);
    }
    return 0;
}