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OI-codes/Hydro/system/H1002/H1002.cpp

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#include <bits/stdc++.h>
using namespace std;
int n, a[1000005], trie[10000005][2], p = 1, ans;
void insert(int u, int x, int b) {
if (!x) return;
if (!trie[u][(x >> b) & 1]) trie[u][(x >> b) & 1] = ++p;
insert(trie[u][(x >> b) & 1], x - (((x >> b) & 1) << b), b - 1);
}
int search(int u, int x) {
int res = 0, t = u;
for (int i = 30; i >= 0; i--) {
if (!t) break;
if (trie[t][!((x >> i) & 1)]) {
res += 1 << i;
t = trie[t][!((x >> i) & 1)];
} else {
t = trie[t][(x >> i) & 1];
}
}
return res;
}
int main() {
scanf("%d", &n);
for (int i = 0; i < n; i++) {
scanf("%d", a + i);
insert(1, a[i], 30);
}
for (int i = 0; i < n; i++) {
ans = max(ans, search(1, a[i]));
}
printf("%d\n", ans);
return 0;
}