Codeforces Round #420 (Div. 2) D

好像并不太懂啊，先挖坑。

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>using namespace std;const int inf=0x7f7f7f7f;int read(){    char ch=getchar();int f=0;    while(ch<'0'||ch>'9') ch=getchar();    while(ch>='0'&&ch<='9')    {f=(f<<1)+(f<<3)+ch-'0';    ch=getchar();}    return f;}int r[10005],c[10005],d[10005]={inf};int n,m,k,jd;bool flag=0,vis[10005];int main(){    int i,id;    n=read();m=read();k=read();    for(int i=1;i<=k;i++)    {        scanf("%d %d",r+i,c+i);        if(r[i]==n&&c[i]==m)        flag=1;        if(r[i]==1&&c[i]==1)        jd=i;        d[i]=inf;    }    if(!flag)    {        r[++k]=++n;        c[k]=++m;    }    d[k]=0;    while(1)    {        id=0;        for(int i=1;i<=k;i++)        {            if(vis[i])            continue;            if(d[i]<d[id])            id=i;        }        if(!id||jd==id)        break;        vis[id]=1;        for(int i=1;i<=k;i++)        {            if(vis[i])            continue;            if(abs(r[i]-r[id])+abs(c[i]-c[id])<=1)            d[i]=d[id];            else if(abs(r[i]-r[id])<=2||abs(c[i]-c[id])<=2)            d[i]=min(d[id]+1,d[i]);        }    }    if(d[jd]==inf)    printf("-1");    else printf("%d",d[jd]);}