hdu1428漫步校园

#include <queue>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <queue>
#include <cstdio>

using namespace std;
int n;
const int maxn = 60;
const int INF = 0x7fffffff;

struct node {
	int x, y;
	int d;
	int mind;
};
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};

node map[maxn][maxn];
queue<node> Q;
long long vis[maxn][maxn];


void input() 
{
	while(!Q.empty()) {
		Q.pop();
	}
	for(int i = 1; i <= n; i++) {
		for(int j = 1; j <= n; j++) {
			scanf("%d", &map[i][j].d);
		    map[i][j].mind = INF;
			map[i][j].x = i;
			map[i][j].y = j;
		}
	}
}

void bfs() 
{
	node tmp, next;
	tmp.d = map[n][n].d;
	tmp.x = n;
	tmp.y = n;
	tmp.mind = map[n][n].d;
	map[n][n].mind = map[n][n].d;//init the beginning 
	Q.push(tmp);
	while(!Q.empty()) 
	{
		node now = Q.front();
		Q.pop();
		for(int i = 0; i < 4; i++) {
			next.x = now.x + dx[i];
			next.y = now.y + dy[i];
			if(next.x<1 || next.x>n || next.y<1 || next.y>n) continue;
			if(map[next.x][next.y].mind > map[now.x][now.y].mind + map[next.x][next.y].d) {
				map[next.x][next.y].mind = map[now.x][now.y].mind + map[next.x][next.y].d;
				Q.push(map[next.x][next.y]);
			}
		}
	}
}

long long dfs(int x, int y) //int wa
{
	if(x==n && y==n) return 1;
	if(vis[x][y]) return vis[x][y];
	int newx, newy;
	for(int i = 0; i < 4; i++) {
		newx = x + dx[i];
		newy = y + dy[i];
		if(newx < 1 || newx > n || newy < 1 || newy > n) continue;
		if(map[x][y].mind > map[newx][newy].mind) {	
			vis[x][y] += dfs(newx, newy);
		}
	}
	return vis[x][y];
}

int main() 
{
	while(scanf("%d", &n) != EOF) {
		input();
		bfs();
		memset(vis, 0, sizeof(vis));
		long long res = dfs(1, 1);
		cout << res << endl;
	}
	return 0;
}