cf888G. Xor-MST(Boruvka最小生成树 Trie树)

#include<bits/stdc++.h>
#define Pair pair<int, int>
#define fi first
#define se second
#define MP(x, y) make_pair(x, y)
#define LL long long
using namespace std;
const int MAXN = 2e5 + 10, B = 31, INF = 1e9 + 7;
inline LL read() {
    char c = getchar(); LL x = 0, f = 1;
    while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x * f;
}
int N, a[MAXN], L[MAXN * 30], R[MAXN * 30], ch[MAXN * 30][2], tot = 0;
void insert(int val, int pos) {
    int now = 0;
    for(int i = B; ~i; i--) {
        int x = val >> i & 1;
        if(!ch[now][x]) ch[now][x] = ++tot, L[tot] = pos, R[tot] = pos;//???ʵ???֮?????λ 
        L[now] = min(L[now], pos); R[now] = max(R[now], pos);
        now = ch[now][x];
    }
}
int Query(int val, int now, int NowBit) {
    LL ans = 1 << (NowBit + 1);
    for(int i = NowBit; ~i; i--) {
        int x = val >> i & 1;
        if(ch[now][x]) now = ch[now][x];
        else ans |= 1 << i, now = ch[now][x ^ 1];
    }
    return ans;
}
LL dfs(int x, int NowBit) {
    LL res = 0;
    if(NowBit == 0)
        return (ch[x][0] && ch[x][1]) ? (a[L[ch[x][0]]] ^ a[R[ch[x][1]]]) : 0;
    //if(NowBit == 0) return ;
    if(ch[x][0] && ch[x][1]) {
        int tmp = INF;
        for(int i = L[ch[x][0]]; i <= R[ch[x][0]]; i++) tmp = min(tmp, Query(a[i], ch[x][1], NowBit - 1));
        res += tmp;
    }
    if(ch[x][0]) res += dfs(ch[x][0], NowBit - 1);
    if(ch[x][1]) res += dfs(ch[x][1], NowBit - 1);
    return res;
}
int main() {
    N = read();
    for(int i = 1; i <= N; i++) a[i] = read();
    sort(a + 1, a + N + 1);
    L[0] = INF; R[0] = 0;
    for(int i = 1; i <= N; i++) insert(a[i], i);
    cout << dfs(0, B);
    return 0;
}