USACO Mother's Milk（bfs）

题目请点我
题解：
水杯倒水的问题非常经典，套路也是一样的，bfs找出全部状态。

这道题的关键在于每次都应该进行六次的倒水尝试，细心一点。PS:三维数组表示状态真的非常方便。

代码实现：

/*
ID: eashion
LANG: C++
TASK: milk3
*/
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <algorithm>
#define MAX 22

using namespace std;

struct state{
    int a,b,c;
};
int A,B,C;
int save[MAX];
queue<state> Q;
int show[MAX][MAX][MAX];
int main()
{
    freopen("milk3.in","r",stdin);
    freopen("milk3.out","w",stdout);
    while( scanf("%d%d%d",&A,&B,&C) != EOF ){
        int pos = 0;
        memset(save,0,sizeof(save));
        memset(show,0,sizeof(show));
        show[0][0][C] = 1;
        state tmp;
        tmp.a = 0;
        tmp.b = 0;
        tmp.c = C;
        Q.push(tmp);
        while( !Q.empty() ){
            state cur;
            cur = Q.front();
            Q.pop();
            if( cur.a == 0 ){
                save[pos] = cur.c;
                pos++;
            }
            state nstate;
            int ta,tb,tc;
            if( cur.a != 0 ){
                ta = cur.a;
                tb = cur.b;
                tc = cur.c;
                if( ta+tb <= B ){
                    tb += ta;
                    ta = 0;
                    tc = cur.c;
                }
                else{
                    ta = ta+tb-B;
                    tb = B;
                    tc = cur.c;
                }
                if( show[ta][tb][tc] != 1 ){
                    nstate.a = ta;
                    nstate.b = tb;
                    nstate.c = tc;
                    Q.push(nstate);
                    show[ta][tb][tc] = 1;
                }
                ta = cur.a;
                tb = cur.b;
                tc = cur.c;
                if( ta+tc <= C ){
                    tc += ta;
                    ta = 0;
                    tb = cur.b;
                }
                else{
                    ta = ta+tc-C;
                    tc = C;
                    tb = cur.b;
                }
                if( show[ta][tb][tc] != 1 ){
                    nstate.a = ta;
                    nstate.b = tb;
                    nstate.c = tc;
                    Q.push(nstate);
                    show[ta][tb][tc] = 1;
                }
            }
            if( cur.b != 0 ){
                ta = cur.a;
                tb = cur.b;
                tc = cur.c;
                if( ta+tb <= A ){
                    ta += tb;
                    tb = 0;
                    tc = cur.c;
                }
                else{
                    tb = ta+tb-A;
                    ta = A;
                    tc = cur.c;
                }
                if( show[ta][tb][tc] != 1 ){
                    nstate.a = ta;
                    nstate.b = tb;
                    nstate.c = tc;
                    Q.push(nstate);
                    show[ta][tb][tc] = 1;
                }
                ta = cur.a;
                tb = cur.b;
                tc = cur.c;
                if( tb+tc <= C ){
                    tc += tb;
                    tb = 0;
                    ta = cur.a;
                }
                else{
                    tb = tb+tc-C;
                    tc = C;
                    ta = cur.a;
                }
                if( show[ta][tb][tc] != 1 ){
                    nstate.a = ta;
                    nstate.b = tb;
                    nstate.c = tc;
                    Q.push(nstate);
                    show[ta][tb][tc] = 1;
                }
            }
            if( cur.c != 0 ){
                ta = cur.a;
                tb = cur.b;
                tc = cur.c;
                if( tc+tb <= B ){
                    tb += tc;
                    tc = 0;
                    ta = cur.a;
                }
                else{
                    tc = tc+tb-B;
                    tb = B;
                    ta = cur.a;
                }
                if( show[ta][tb][tc] != 1 ){
                    nstate.a = ta;
                    nstate.b = tb;
                    nstate.c = tc;
                    Q.push(nstate);
                    show[ta][tb][tc] = 1;
                }
                ta = cur.a;
                tb = cur.b;
                tc = cur.c;
                if( ta+tc <= A ){
                    ta += tc;
                    tc = 0;
                    tb = cur.b;
                }
                else{
                    tc = ta+tc-A;
                    ta = A;
                    tb = cur.b;
                }
                if( show[ta][tb][tc] != 1 ){
                    nstate.a = ta;
                    nstate.b = tb;
                    nstate.c = tc;
                    Q.push(nstate);
                    show[ta][tb][tc] = 1;
                }
            }
        }
        sort(save,save+pos);
        for( int i = 0; i < pos; i++ ){
            if( i != pos-1 ){
                printf("%d ",save[i]);
            }
            else{
                printf("%d\n",save[i]);
            }
        }
    }
    return 0;
}