bzoj4668: 冷战 并查集按秩合并

Posted 2020-12-05 sssy

题目链接

bzoj4668: 冷战

题解

按秩合并并查集,每次增长都是小集合倍数的两倍以上,层数不超过logn
查询路径最大值
LCT同解

代码

#include<bits/stdc++.h> 
using namespace std; 
inline int read() { 
    int x = 0,f = 1;
    char c = getchar(); 
    while(c < '0' || c > '9')c = getchar(); 
    while(c <= '9' && c >= '0')x = x * 10 + c - '0',c = getchar(); 
    return x * f; } 
int n,m; 
const int maxn = 5000007; 
int cnt = 0 ,fa[maxn],deep[maxn],siz[maxn],v[maxn]; 
int find(int x)  { 
    if(fa[x] != x) { 
        int f = find(fa[x]); 
        deep[x] = deep[fa[x]] + 1; 
        return f;   
    } else return x; 
} 
void Union(int x,int y,int C) { 
    int f1 = find(x),f2 = find(y);  
    if(f1 == f2) return ;  
    if(siz[f1] > siz[f2]) fa[f2] = f1,v[f2] = C,siz[f1] += siz[f2]; 
    else fa[f1] = f2,v[f1] = C,siz[f2] += siz[f1]; 
} 
int query(int x,int y) {
    int f1 = find(x),f2 = find(y); 
    if(f1 != f2)return 0; 
    int ret = 0 ; 
    for(;x != y;) { 
        if(deep[x] < deep[y]) swap(x,y); 
        ret = max(ret,v[x]),x = fa[x]; 
    } return ret; 
} 
int main() { 
    n = read(),m = read(); 
    for(int i = 1;i <= n;++ i) fa[i] = i,siz[i] = 1; 
    int ans = 0; 
    for(int op,u,v,i = 1;i <= m;++ i) { 
        op = read();u = read() ^ ans,v = read() ^ ans; 
        if(!op) { 
            Union(u,v,++ cnt); 
        } else printf("%d
",ans = query(u,v)); 
    } 
    return 0; 
} 
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