P1443 马的遍历

同样是一个bfs水题。。。

#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> St;
St start;
queue<St> sts;
map<St, int> dist;
int n, m, x, y;
const int dx[] = {-1, 1, 2, 2, 1, -1, -2, -2};
const int dy[] = {2, 2, 1, -1, -2, -2, -1, 1};
//-----------------
void bfs() {
	sts.push(start);
	while(!sts.empty()) {
		St now = sts.front(); sts.pop();
		int nowx = now.first;
		int nowy = now.second;
		for(int i = 0; i < 8; i++) {
			int newx = nowx + dx[i];
			int newy = nowy + dy[i];
			if(newx > 0 && newx <= n && newy > 0 && newy <= m) {
				St neww(newx, newy);
				if(dist.count(neww)) continue;
				dist[neww] = dist[now] + 1;
				sts.push(neww);
			}
		}
	}
}
void output() {
	for(int i = 1; i <= n; i++) {
		for(int j = 1; j <= m; j++) {
			if(i==x&&j==y) printf("%-5d", 0);
			else {
				St now(i, j);
				int d = dist[now];
				if(d) printf("%-5d", d);
				else printf("%-5d", -1);
			}
		}
		cout << endl;
	}
}
//-----------------
int main() {
	cin >> n >> m >> x >> y;
	start.first = x;
	start.second = y;
	bfs();
	output();
	return 0;
}

不过莫名其妙不知道为什么最后一个点没有过