hdu 1495 非常可樂（bfs）

大家一定覺的運動以後喝可樂是一件很愜意的事情，但是seeyou卻不這麼認爲。因爲每次當seeyou買了可樂以後，阿牛就要求和seeyou一起分享這一瓶可樂，而且一定要喝的和seeyou一樣多。但seeyou的手中只有兩個杯子，它們的容量分別是N 毫升和M 毫升 可樂的體積爲S （S<101）毫升　(正好裝滿一瓶) ，它們三個之間可以相互倒可樂 (都是沒有刻度的，且 S==N+M，101＞S＞0，N＞0，M＞0) 。聰明的ACMER你們說他們能平分嗎？如果能請輸出倒可樂的最少的次數，如果不能輸出”NO”。

Input
三個整數 : S 可樂的體積 , N 和 M是兩個杯子的容量，以”0 0 0”結束。

Output
如果能平分的話請輸出最少要倒的次數，否則輸出”NO”。
Sample Input

7 4 3
4 1 3
0 0 0

Sample Output

NO
3

題解：
每一步一共有六種狀態，分別是s->n, s->m, n->s, n->m, m->s, m->s;
將每一步的六種狀態放入隊列即可~要記得路徑標記，不然會死循環的~~

#include<bits/stdc++.h>
using namespace std;

int s, n, m;
bool vis[110][110][110];

struct bu{
    int x, y, z, step;
};

int bfs(int c){
    queue<bu> q;
    bu a, ne;
    int t;
    a.x = s; a.y = a.z = a.step = 0;
    q.push(a);
    vis[a.x][a.y][a.z] = 1;
    while(!q.empty()){
        a = q.front();
        q.pop();
        if(a.x == c && a.y == c){
            //cout << "a.step = " <<a.step << endl;
            return a.step;
        }
        if(a.x && a.y != n){//s - > n
            t = n - a.y;
            if(t > a.x){
                ne.y = a.y + a.x;
                ne.x = 0;
            }
            else{
                ne.y = n;
                ne.x = a.x - t;
            }
            ne.z = a.z;
            ne.step = a.step + 1;
            if(!vis[ne.x][ne.y][ne.z]){
                q.push(ne);
             //   cout << "ne.x = " << ne.x << " ne.y = " << ne.y << " ne.z = " << ne.z << " ne.step = " << ne.step << endl;
                vis[ne.x][ne.y][ne.z] = 1;
            }
        }
        if(a.x && a.z != m){//s -> b
            t = m - a.z;
            if(t > a.x){
                ne.z = a.z + a.x;
                ne.x = 0;
            }
            else{
                ne.z = m;
                ne.x = a.x - t;
            }
            ne.y = a.y;
            ne.step = a.step + 1;
            if(!vis[ne.x][ne.y][ne.z]){
                q.push(ne);
             //   cout << "ne.x = " << ne.x << " ne.y = " << ne.y << " ne.z = " << ne.z << " ne.step = " << ne.step << endl;
                vis[ne.x][ne.y][ne.z] = 1;
            }
        }
        if(a.y && a.z != m){//a -> b
            t = m - a.z;
            if(t > a.y){
                ne.z = a.z + a.y;
                ne.y = 0;
            }
            else{
                ne.z = m;
                ne.y = a.y - t;
            }
            ne.x = a.x;
            ne.step = a.step + 1;
            if(!vis[ne.x][ne.y][ne.z]){
                q.push(ne);
            //    cout << "ne.x = " << ne.x << " ne.y = " << ne.y << " ne.z = " << ne.z << " ne.step = " << ne.step << endl;
                vis[ne.x][ne.y][ne.z] = 1;
            }
        }
        if(a.z && a.y != n){//b -> a
            t = n - a.y;
            if(t > a.z){
                ne.y = a.z + a.y;
                ne.z = 0;
            }
            else{
                ne.y = n;
                ne.z = a.z - t;
            }
            ne.x = a.x;
            ne.step = a.step + 1;
            if(!vis[ne.x][ne.y][ne.z]){
                q.push(ne);
            //    cout << "ne.x = " << ne.x << " ne.y = " << ne.y << " ne.z = " << ne.z << " ne.step = " << ne.step << endl;
                vis[ne.x][ne.y][ne.z] = 1;
            }
        }
        if(a.y && a.x != s){//a -> s
            t = s - a.x;
            if(t > a.y){
                ne.x = a.x + a.y;
                ne.y = 0;
            }
            else{
                ne.x = s;
                ne.y = a.y - t;
            }
            ne.z = a.z;
            ne.step = a.step + 1;
            if(!vis[ne.x][ne.y][ne.z]){
                q.push(ne);
               // cout << "ne.x = " << ne.x << " ne.y = " << ne.y << " ne.z = " << ne.z << " ne.step = " << ne.step << endl;
                vis[ne.x][ne.y][ne.z] = 1;
            }
        }
        if(a.y && a.x != s){//b -> s
            t = s - a.x;
            if(t > a.z){
                ne.x = a.z + a.x;
                ne.z = 0;
            }
            else{
                ne.x = s;
                ne.z = a.z - t;
            }
            ne.y = a.y;
            ne.step = a.step + 1;
            if(!vis[ne.x][ne.y][ne.z]){
                q.push(ne);
               // cout << "ne.x = " << ne.x << " ne.y = " << ne.y << " ne.z = " << ne.z << " ne.step = " << ne.step << endl;
                vis[ne.x][ne.y][ne.z] = 1;
            }
        }
    }
    return 0;
}

int main(){
    while(scanf("%d%d%d", &s, &n, &m)!=EOF && s!=0 || n!=0 || m!=0){
        if(n < m) swap(n, m);
        memset(vis, 0, sizeof(vis));
        if(s%2){
            printf("NO\n");
        }
        else{
            int sum = bfs(s/2);
            if(sum == 0)
                printf("NO\n");
            else{
                printf("%d\n", sum);
            }
        }
    }
    return 0;
}