题解

#include<iostream>
#include<cstring>
#include<queue>
using namespace std;
const int N = 105;

struct Node{
	
	int x, y, t;
	string step;
	
};
int n, m, k;
bool vis[N] [N];
queue<Node> q;

int main() {
	
	cin >> n >> m >> k;
	q.push({ 0, 0, 0,  "" });
	vis[0][0] = true;
	
	while( !q.empty() ) {
		
		Node now = q.front(), nt;
		if( now.x == k || now.y == k ){
			
			cout << now.t << '\n' << now.step;
			return 0; 
			
		}
		q.pop();
		
		nt.x = n, nt.y = now.y, nt.t = now.t + 1, nt.step = now.step + "FILL(1)\n";
		if( !vis[nt.x][nt.y] ) vis[nt.x][nt.y] = true, q.push(nt);
		
		nt.x = now.x, nt.y = m, nt.t = now.t + 1, nt.step = now.step + "FILL(2)\n"; 
		if( !vis[nt.x][nt.y] ) vis[nt.x][nt.y] = true, q.push(nt);
		
		nt.x = 0, nt.y = now.y, nt.t = now.t + 1, nt.step = now.step + "DROP(1)\n";
		if( !vis[nt.x][nt.y] ) vis[nt.x][nt.y] = true, q.push(nt);
		
		nt.x = now.x, nt.y = 0, nt.t = now.t + 1, nt.step = now.step + "DROP(2)\n";
		if( !vis[nt.x][nt.y] ) vis[nt.x][nt.y] = true, q.push(nt);
		
		nt.x = max( 0, now.x + now.y - m ), nt.y = min( m, now.x + now.y  ), nt.t = now.t + 1, nt.step = now.step + "POUR(1,2)\n";
		if( !vis[nt.x][nt.y] ) vis[nt.x][nt.y] = true, q.push(nt);
		
		nt.x = min( n, now.x + now.y  ), nt.y = max( 0, now.x + now.y - n ), nt.t = now.t + 1, nt.step = now.step + "POUR(2,1)\n";
		if( !vis[nt.x][nt.y] ) vis[nt.x][nt.y] = true, q.push(nt);
		
	}
		
	cout << "impossible";
		
}