poj 3414 Pots BFS

Description

You are given two pots, having the volume of A and B liters respectively. The following operations can be performed:

FILL(i) fill the pot i (1 ≤ i ≤ 2) from the tap;
DROP(i) empty the pot i to the drain;
POUR(i,j) pour from pot i to pot j; after this operation either the pot j is full (and there may be some water left in the pot i),
or the pot i is empty (and all its contents have been moved to the pot j).

Write a program to find the shortest possible sequence of these operations that will yield exactly C liters of water in one of the pots.

Input

On the first and only line are the numbers A, B, and C. These are all integers in the range from 1 to 100 and C≤max(A,B).

Output

The first line of the output must contain the length of the sequence of operations K. The following K lines must each describe one operation. If there are several sequences of minimal
length, output any one of them. If the desired result can’t be achieved, the first and only line of the file must contain the word ‘impossible’.

Sample Input

3 5 4

Sample Output
6
FILL(2)
POUR(2,1)
DROP(1)
POUR(2,1)
FILL(2)
POUR(2,1)

题意及分析：
有两个容器，给出容积。进行题目给出的三种操作。使得其中一个储水量达到指定要求。
关键是对每一步状态的表示。其实是第一次处理这种bfs问题。就是用很多量来表示某一个状态。详细地表示在下面有。
大体思路就是用结构体存每一个状态，vis[][]数组表示两个容器的水的体积。找到目标状态后，递归输出。
心得就是对于自己的想法要敢于尝试。
AC代码：