POJ 3248 Catch That Cow

http://poj.org/problem?id=3278

二维BFS

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <queue>
#define READ() freopen("in.txt", "r", stdin);

using namespace std;

struct Loc
{
    int x, step;
    Loc () {}
    Loc(int x, int step) : x(x), step(step) {}
};

int N, K;
bool use[100007];
bool OK(int x)
{
    if (x < 0 || x > 100000 ) return false;
    else return true;
}
int bfs()
{
    queue<Loc> que;
    que.push(Loc(N, 0));
    while (!que.empty())
    {
        Loc crt = que.front();
        que.pop();
        if(use[crt.x]) continue;
        use[crt.x] = true;
        int nx = crt.x - 1;
        if (OK(nx) && !use[nx])
        {
            if (nx == K) return crt.step+1;
            else que.push(Loc(nx, crt.step+1));
        }
        nx = crt.x + 1;
        if (OK(nx))
        {
            if (nx == K && !use[nx]) return crt.step+1;
            else que.push(Loc(nx, crt.step+1));
        }
        nx = 2*crt.x;
        if (OK(nx) && !use[nx])
        {
            if (nx == K) return crt.step+1;
            else que.push(Loc(nx, crt.step+1));
        }
    }
}
int main()
{
    //READ()
    scanf("%d%d", &N, &K);
    if (N == K) //有N == K的坑点 严谨一点
    {
        cout << 0 << endl;
        return 0;
    }
    memset(use, 0, sizeof(use));
    int ans = bfs();
    cout << ans << endl;
    return 0;
}