洛谷 P1196 银河英雄传说

带权并查集

题目传送门

sum[i]记录i这列有多少个战舰。num[i]记录i前面有多少个战舰。找爸爸的时候更新即可。

代码：

#include<cstdio>
#include<algorithm>
#include<cstring>
#define MAXN 30000
using namespace std;
int fa[MAXN+5],num[MAXN+5],sum[MAXN+5];
int n;
char readc(){
    static char buf[100000],*l=buf,*r=buf;
    if (l==r) r=(l=buf)+fread(buf,1,100000,stdin);
    if (l==r) return EOF;
    else return *l++;
}
inline int _read(){
    int num=0; char ch=readc();
    while ((ch<'0'||ch>'9')&&ch!='M'&&ch!='C') ch=readc();
    if (ch=='M'||ch=='C') return (int)ch;
    while (ch>='0'&&ch<='9'){ num=num*10+ch-48; ch=readc(); }
    return num;    
}
int findfather(int x){
    if (fa[x]==x)
        return x;
    int fat=fa[x];
    fa[x]=findfather(fa[x]);
    num[x]+=num[fat];
    return fa[x];
}
int main(){
    n=_read();
    for (int i=1;i<=MAXN;i++){
        fa[i]=i;
        sum[i]=1;
    }
    while (n--){
        int flag=_read(),x=_read(),y=_read();
        if (flag=='M'){
            int fx=findfather(x),fy=findfather(y);
            fa[fx]=fy;
            num[fx]+=sum[fy];
            sum[fy]+=sum[fx];
        }
        if (flag=='C'){
            int fx=findfather(x),fy=findfather(y);
            if (fx!=fy)
                printf("-1\n");
            else
                printf("%d\n",abs(num[y]-num[x])-1);
        }
    }
    return 0;
}