CodeForces - 1447F Xor Tree

传送门：CodeForces - 1447F

思路分析

将所有数插入字典树，对于同一个节点的两个子树，子树内部的点肯定互相连边，要使得有一条边跨过这两个子树，那么其中一个子树一定只选了一个点，在字典树上分治即可

AC代码

#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define fun function
#define sz(x) (x).size()
#define lowbit(x) (x)&(-x)
#define all(x) (x).begin(),(x).end()
#define mem(a,b) memset(a,b,sizeof(a))

namespace FastIO {
#define BUF_SIZE 100000
#define OUT_SIZE 100000
    bool IOerror=0;
    inline char nc() {
        static char buf[BUF_SIZE],*p1=buf+BUF_SIZE,*pend=buf+BUF_SIZE;
        if(p1==pend) {
            p1=buf;
            pend=buf+fread(buf,1,BUF_SIZE,stdin);
            if(pend==p1) {
                IOerror=1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool blank(char ch) {
        return ch==' '||ch=='\n'||ch=='\r'||ch=='\t';
    }
    template<class T> inline bool read(T &x) {
        bool sign=0;
        char ch=nc();
        x=0;
        for(; blank(ch); ch=nc());
        if(IOerror)return false;
        if(ch=='-')sign=1,ch=nc();
        for(; ch>='0'&&ch<='9'; ch=nc())x=x*10+ch-'0';
        if(sign)x=-x;
        return true;
    }
    template<class T,class... U>bool read(T& h,U&... t) {
        return read(h)&&read(t...);
    }
#undef OUT_SIZE
#undef BUF_SIZE
};
using namespace std;
using namespace FastIO;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

typedef long long ll;
typedef pair<int,int> pii;
typedef unsigned long long ull;

const int INF = 0x3f3f3f3f;
const int N = 2e5+10;

int tree[N*32][2],cnt;

void ins(int val){
    int x = 0;
    for(int i=30;i>=0;i--){
        int s = (val>>i)&1;
        if(!tree[x][s]) tree[x][s] = ++cnt;
        x = tree[x][s];
    }
}

int dfs(int x,int pos){
    if(pos == -1) return 1;
    int l = tree[x][0];
    int r = tree[x][1];
    if(l && r) return max(dfs(l,pos-1),dfs(r,pos-1))+1;
    if(l) return dfs(l,pos-1);
    if(r) return dfs(r,pos-1);
}

int main() {

#ifdef xiaofan
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
#endif

    int n;
    cin>>n;
    for(int i=1;i<=n;i++) {
        int x;
        cin>>x;
        ins(x);
    }
    cout<<n-dfs(0,30)<<endl;




    return 0;
}