学完堆以后的第一件事：

#include <iostream>
#include <cstdio>
//#include <queue>
#include <vector>
using namespace std;
struct Point{
	int x, y, step;
};
bool cmp(Point a, Point b){
	return a.step < b.step;
}
struct priority_queue{
	vector <Point> __data;
	void push(Point tmp){
		__data.push_back(tmp);
		int i = __data.size();
		while(i / 2 >= 1 && !cmp(__data[i / 2 - 1], __data[i - 1])){
			swap(__data[i - 1], __data[i / 2 - 1]);
			i = i / 2;
		}
	}
	Point top(){
		return __data[0]; 
	}
	void pop(){
		__data[0] = __data.back();
		__data.pop_back();
		int i = 1;
		while(i * 2 <= __data.size()){
			int j = i * 2;
			if(j < __data.size() && cmp(__data[j], __data[j - 1])) j++;
			if(!cmp(__data[j - 1], __data[i - 1])) return;
			swap(__data[i - 1], __data[j - 1]);
			i = j;
		}
	}
	bool empty(){
		return __data.empty();
	}
	int size(){
		return __data.size();
	}
};
int n, m, x1, y1, x2, y2;
bool vis[45][45];
char mp[45][45];
int dir[4][2] = {-1, 0, 0, -1, 0, 1, 1, 0};
priority_queue q;
bool check(int x, int y){
	if(x < 1 || x > n) return 0;
	if(y < 1 || y > m) return 0;
	if(mp[x][y] == '#') return 0;
	if(vis[x][y]) return 0;
	return 1;
}
void bfs(int x, int y){
	vis[x][y] = 1;
	bool flag = 0;
	int mx = 0x3f3f3f3f;
	q.push({x, y, 0}); 
	while(!q.empty()){
		Point head = q.top();
		q.pop();
		//cout << head.x << ' ' << head.y << ' ' << head.step << endl; 
		if(head.x == x2 && head.y == y2){
			//cout << mx << endl;
			mx = min(mx, head.step);
			flag = 1;
			continue;
		}
		for(int i = 0; i < 4; i++){
			int xx = head.x + dir[i][0], yy = head.y + dir[i][1];
			if(check(xx, yy)){
				if(mp[xx][yy] != '.' && mp[xx][yy] != 'W') q.push({xx, yy, head.step + 1 + mp[xx][yy] - '0'});
				else q.push({xx, yy, head.step + 1});
				vis[xx][yy] = 1;
			}
		}
	}
	if(!flag) cout << "IMPOSSIBLE";
	else cout << mx;
}
int main(){
	cin >> n >> m;
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= m; j++){
			cin >> mp[i][j];
			if(mp[i][j] == 'Z') x1 = i, y1 = j;
			if(mp[i][j] == 'W') x2 = i, y2 = j;
			
		}
	}//cout << x1 << ' ' << y1 << ' ' << x2 << ' ' << y2 << endl;
	bfs(x1, y1);

	return 0;
}