【HDU-1295】非常可乐（bfs）

Problem Description

大家一定觉的运动以后喝可乐是一件很惬意的事情，但是seeyou却不这么认为。因为每次当seeyou买了可乐以后，阿牛就要求和seeyou一起分享这一瓶可乐，而且一定要喝的和seeyou一样多。但seeyou的手中只有两个杯子，它们的容量分别是N 毫升和M 毫升 可乐的体积为S （S<101）毫升　(正好装满一瓶) ，它们三个之间可以相互倒可乐 (都是没有刻度的，且 S==N+M，101＞S＞0，N＞0，M＞0) 。聪明的ACMER你们说他们能平分吗？如果能请输出倒可乐的最少的次数，如果不能输出”NO”。

Input

三个整数 : S 可乐的体积 , N 和 M是两个杯子的容量，以”0 0 0”结束。

Output

如果能平分的话请输出最少要倒的次数，否则输出”NO”。

Sample Input

7 4 3
4 1 3
0 0 0

Sample Output

NO
3

题目大意

中文题

思路

A B C三个杯子，总共有12种情况
A到B够倒和不够倒两种；
A到C够倒和不够倒两种；
B到A够倒和不够倒两种；
B到C够倒和不够倒两种；
C到A够倒和不够倒两种；
C到B够倒和不够倒两种；
bfs这12中情况就可以了；

代码

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

using namespace std;

int S,N,M;
int NUMBER;
bool Can;
int vis[101][101][101];

struct Tri
{
    int s;
    int n;
    int m;
    int number;
};


bool IsOver( int s,int n,int m )
{
    if( (s == m && s != 0 && n == 0 )|| ( s == n && n != 0 && m==0 )|| ( m == n && m !=0 && s == 0 ) )
        return true;
    return false;
}

bool IsLeagal( int s,int n,int m )
{
    if( s < 0 || s > S || n < 0 || n > N || m < 0 || m > M )
        return false;
    return true;
}

void bfs()
{
    queue<Tri> Ways;
    memset( vis,0,sizeof( vis));

    vis[S][0][0] = 1;

    Tri Now,Next1,Next2,Next3,Next4,Next5,Next6;
    Now.s = S;
    Now.n = 0;
    Now.m = 0;
    Now.number  = 0;
    Ways.push ( Now );
    while( !Ways.empty ())
    {
        Now.s = Ways.front ().s ;
        Now.n = Ways.front ().n ;
        Now.m = Ways.front ().m ;
        Now.number = Ways.front ().number ;
        Ways.pop ();

        if( Can )
            return;
        /* 从第一个杯子到给第二个杯子 */
        if( Now.s > ( N - Now.n) )
        {   Next1.s = Now.s - ( N - Now.n);
            Next1.n = N;
            Next1.m = Now.m;
            Next1.number = Now.number + 1;}
        else 
        {   Next1.s = 0;
            Next1.n = Now.n + Now.s ;
            Next1.m = Now.m;
            Next1.number = Now.number + 1;}
        if( IsLeagal( Next1.s ,Next1.n ,Next1.m ) && !vis[Next1.s ][Next1.n ][Next1.m ])
        {
            vis[Next1.s ][Next1.n ][Next1.m ] = 1;
            if( IsOver( Next1.s ,Next1.n ,Next1.m ))
            {   Can = true;
                NUMBER = Next1.number ;
                return; }
            Ways.push ( Next1 );
        }

        /* 从第一个杯子到给第三个杯子 */
        if( Now.s > ( M - Now.m ) )
        {   Next2.s = Now.s - ( M - Now.m );
            Next2.n = Now.n;
            Next2.m = M;
            Next2.number = Now.number + 1;}
        else
        {   Next2.s = 0;
            Next2.n = Now.n;
            Next2.m = Now.s + Now.m;
            Next2.number = Now.number + 1;}
        if( IsLeagal( Next2.s ,Next2.n ,Next2.m ) && !vis[Next2.s ][Next2.n ][Next2.m ])
        {
            vis[Next2.s ][Next2.n ][Next2.m ] = 1;
            if( IsOver( Next2.s ,Next2.n,Next2.m ))
            {   Can = true;
                NUMBER =  Next2.number  ;
                return; }
            Ways.push ( Next2 );
        }

        /* 从第二个杯子到给第一个杯子 */
        if( Now.n > ( S - Now.s ) )
        {   Next3.s = S;
            Next3.n = Now.n - ( S - Now.s );
            Next3.m = Now.m;
            Next3.number = Now.number + 1;}
        else
        {   Next3.s = Now.s + Now.n ;
            Next3.n = 0;
            Next3.m = Now.m;
            Next3.number = Now.number + 1;}
        if( IsLeagal( Next3.s ,Next3.n ,Next3.m ) && !vis[Next3.s ][Next3.n ][Next3.m ])
        {
            vis[Next3.s ][Next3.n ][Next3.m ] = 1;
            if( IsOver( Next3.s ,Next3.n ,Next3.m ))
            {   Can = true;
                NUMBER = Next3.number ;
                return; }
            Ways.push ( Next3 );
        }

        /* 从第二个杯子到给第三个杯子 */
        if( Now.n > ( M - Now.m ))
        {   Next4.s = Now.s ;
            Next4.n = Now.n - ( M - Now.m );
            Next4.m = M;
            Next4.number = Now.number + 1;}
        else
        {   Next4.s = Now.s ;
            Next4.n = 0;
            Next4.m = Now.n + Now.m ;
            Next4.number = Now.number + 1;}
        if( IsLeagal( Next4.s ,Next4.n ,Next4.m ) && !vis[Next4.s ][Next4.n ][Next4.m ])
        {
            vis[Next4.s ][Next4.n ][Next4.m ] = 1;
            if( IsOver( Next4.s ,Next4.n ,Next4.m ))
            {   Can = true;
                NUMBER = Next4.number ;
                return; }
            Ways.push ( Next4 );
        }

        /* 从第三个杯子到给第一个杯子 */
        if( Now.m - ( S - Now.s ) )
        {   Next5.s = S;
            Next5.n = Now.n ;
            Next5.m = Now.m - ( S - Now.s );
            Next5.number = Now.number + 1;}
        else
        {   Next5.s = Now.s + Now.m ;
            Next5.n = Now.n ;
            Next5.m = 0;
            Next5.number = Now.number + 1;}
        if( IsLeagal( Next5.s ,Next5.n ,Next5.m ) && !vis[Next5.s ][Next5.n ][Next5.m ])
        {
            vis[Next5.s ][Next5.n ][Next5.m ] = 1;
            if( IsOver( Next5.s ,Next5.n ,Next5.m ))
            {   Can = true;
                NUMBER = Next5.number ;
                return; }
            Ways.push ( Next5 );
        }

        /* 从第三个杯子到给第二个杯子 */
        if( Now.m > ( N - Now.n ))
        {   Next6.s = Now.s;
            Next6.n = N;
            Next6.m = Now.m - ( N - Now.n );
            Next6.number = Now.number + 1;}
        else
        {   Next6.s = Now.s;
            Next6.n = Now.m + Now.n ;
            Next6.m = 0;
            Next6.number = Now.number + 1;}
        if( IsLeagal( Next6.s ,Next6.n ,Next6.m ) && !vis[Next6.s ][Next6.n ][Next6.m ])
        {
            vis[Next6.s ][Next6.n ][Next6.m ] = 1;
            if( IsOver( Next6.s ,Next6.n ,Next6.m ))
            {   Can = true;
                NUMBER = Next6.number ;
                return; }
            Ways.push ( Next6 );
        }

    }
}
int main()
{
    while( cin >> S >> N >> M )
    {
        if( S == 0 && N == 0 && M == 0 ) break;
        if( N > M )
        {
            int tmp;
            tmp = N;
            N =M;
            M = tmp;
        }
        if( S % 2 != 0 )
        {
            cout<<"NO"<<endl;
            continue;
        }
        Can = false;
        bfs();
        if( Can )
            cout<< NUMBER <<endl;   
        else 
            cout<<"NO"<<endl;
    }
    return 0;
}