poj3414-水杯

题目链接 http://vjudge.net/problem/15208

解题思路

隐式图搜索，只有两个水杯状态表示也比较方便。

代码

#include<stdio.h>
#include<string.h>
#define MAX_SIZE 105
#define QUE_SIZE 10005
struct water {
    int a, b;
    int before;
    char step[20];
    int now;
};
bool ZT[MAX_SIZE][MAX_SIZE];
water Q[QUE_SIZE];
int A, B, C;
int search(int x, int y)
{
    int front = -1, rear = -1;
    Q[++rear].a = x; Q[rear].b = y; ZT[x][y] = true;
    Q[rear].before = -1; Q[rear].now = 0;
    while(front != rear) {
        water u = Q[++front];
        if(u.a == C || u.b == C) return front;
        if(!ZT[A][u.b])
            { Q[++rear].a = A; Q[rear].b = u.b; strcpy(Q[rear].step, "FILL(1)");
            Q[rear].now=u.now+1; Q[rear].before = front; ZT[A][u.b] = true; }
        if(!ZT[u.a][B])
            { Q[++rear].a = u.a; Q[rear].b = B; strcpy(Q[rear].step, "FILL(2)");
            Q[rear].now=u.now+1; Q[rear].before = front; ZT[A][u.b] = true; }
        if(!ZT[0][u.b])
            { Q[++rear].a = 0; Q[rear].b = u.b; strcpy(Q[rear].step, "DROP(1)");
            Q[rear].now=u.now+1; Q[rear].before = front; ZT[0][u.b] = true; }
        if(!ZT[u.a][0])
            { Q[++rear].a = u.a; Q[rear].b = 0; strcpy(Q[rear].step, "DROP(2)");
            Q[rear].now=u.now+1; Q[rear].before = front; ZT[u.a][0] = true; }
        int addW = A-u.a < u.b ? A-u.a : u.b;
        int leftW = A-u.a < u.b ? u.b-A+u.a : 0;
        if(!ZT[u.a+addW][leftW])
            { Q[++rear].a = u.a+addW; Q[rear].b = leftW; strcpy(Q[rear].step, "POUR(2,1)");
            Q[rear].now=u.now+1; Q[rear].before = front; ZT[u.a+addW][leftW] = true; }
        addW = B-u.b < u.a ? B-u.b : u.a;
        leftW = B-u.b < u.a ? u.a-B+u.b : 0;
        if(!ZT[leftW][u.b+addW])
            { Q[++rear].a = leftW; Q[rear].b = u.b+addW; strcpy(Q[rear].step, "POUR(1,2)");
            Q[rear].now=u.now+1; Q[rear].before = front; ZT[leftW][u.b+addW] = true; }
    }
    return -1;
}
void print(int nowStep)
{
    if(nowStep == 0) return ;
    print(Q[nowStep].before);
    printf("%s\n", Q[nowStep].step);
}
int main()
{
    scanf("%d%d%d", &A, &B, &C);
    int Index = search(0,0);
    if(Index == -1) printf("impossible\n");
    else {
        printf("%d\n", Q[Index].now);
        print(Index);
    }
    return 0;
}