P140 Catch That Cow

深度优先搜索，队列

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>

using namespace std;

const int MAXN = 100001;

struct Status{
    int n, t;
    Status(int n, int t): n(n), t(t) {}
};

bool visited[MAXN];

int BFS(int n, int k){
    queue<Status> myQueue;
    myQueue.push(Status(n, 0));
    visited[n] = true;
    while(!myQueue.empty()){
        Status now = myQueue.front();
        myQueue.pop();
        if(now.n == k){
            return now.t;
        }
        for(int i = 0; i < 3; i++){
            Status next(now.n, now.t + 1);
            if(i == 0){
                next.n += 1;
            }else if(i == 1){
                next.n -= 1;
            }else{
                next.n *= 2;
            }
            if(next.n < 0 || next.n >= MAXN || visited[next.n] == true){
                continue;
            }
            myQueue.push(next);
            visited[next.n] = true;
        }
    }
}

int main(){
    int n, k;
    while(cin >> n >> k){
        memset(visited, false, sizeof(visited)); //!!!!!!一定要记得初始化
        printf("%d\n", BFS(n, k));
    }
    return 0; 
}