Horse Pro（带负坐标的bfs搜索）

Horse Pro

bfs搜索，但图中存在负值坐标，两种方法解决。

• 用数组标记，将原点设为300，300
• 用map标记

http://oj.jxust.edu.cn/contest/Problem?id=1689&pid=5

#include <iostream>
#include <cstdio>
#include <queue>
using namespace std;
typedef long long ll;
const int maxn = 100000 + 5;

int bx,by,e2,ey;
int vis[605][605];
int dir[8][2]={2,1,2,-1,-2,1,-2,-1,1,2,-1,2,1,-2,-1,-2};
struct Node
{
    int x;
    int y;
    int len;
};

int bfs()
{
    Node next;
    next.x=bx;next.y=by;next.len=0;
    queue<Node> q;
    q.push(next);
    while(!q.empty())
    {
        Node front;
        front =q.front();
        if(front.len>100) return -1;
        q.pop();
        for(int i=0;i<8;i++)
        {
            next.x=front.x+dir[i][0],next.y=front.y+dir[i][1],next.len=front.len+1;
            if(vis[next.x][next.y]) continue;
            if(next.x==e2&&next.y==ey) return next.len;
            q.push(next);
            vis[next.x][next.y]=1;
        }
    }
    return -1;
}

int main() {
    scanf("%d%d%d%d",&bx,&by,&e2,&ey);
    e2=e2-bx+300;ey=ey-by+300;
    bx=300;by=300;
    int res=bfs();
    printf("%d\n",res);
    return 0;
}

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
using namespace std;

#define mem(a,b) memset(a,b,sizeof(a))
#define ll long long
const int maxn = 100100;
const int inf = 0x3f3f3f3f;
const int M = 1e9+7;
int to[8][2] = {2,1,2,-1,-2,1,-2,-1,1,2,-1,2,1,-2,-1,-2};
int a,b,c,d;
struct node
{
    int x,y,z;
};

map<pair<int,int>, int> m;

int bfs()
{
    node now,nex;
    now.x = a,now.y= b,now.z = 0;
    std::queue<node> q;
    q.push(now);
    while(!q.empty())
    {
        now = q.front();
        q.pop();
        if(now.x == c && now.y==d) return now.z;
        if(now.z > 100) break;
        for(int i = 0; i < 8; i++)
        {
            nex.x = now.x+to[i][0];
            nex.y = now.y+to[i][1];
            if(m[make_pair(nex.x,nex.y)]) continue;
            m[make_pair(nex.x,nex.y)]=1;
            nex.z = now.z+1;
            q.push(nex);
        }
    }
    return -1;
}

int main()
{
    scanf("%d%d%d%d", &a,&b,&c,&d);
    c=c-a;d=d-b;
    a=0,b=0;
    printf("%d\n", bfs());
    return 0;
}