体面描述
Today, as a friendship gift, Bakry gave Badawy n integers a1,a2,…,an and challenged him to choose an integer X such that the value max1≤i≤n(ai⊕X) is minimum possible, where ⊕ denotes the bitwise XOR operation.
As always, Badawy is too lazy, so you decided to help him and find the minimum possible value of max1≤i≤n(ai⊕X).
Input
The first line contains integer n (1≤n≤105).
The second line contains n integers a1,a2,…,an (0≤ai≤230−1).
Output
Print one integer — the minimum possible value of max1≤i≤n(ai⊕X).
Examples
Input
3
1 2 3
Output
2
Input
2
1 5
Output
4
Note
In the first sample, we can choose X=3.
In the second sample, we can choose X=5.
问题简述
分治，问题分析以后补
#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5;
typedef long long ll;
typedef unsigned long long ull;
const int INF = 0x3f3f3f3f;
ll n;
vector<int> a;
ll solve(vector<int> &c, int idx)
{
if (idx < 0 || !c.size())
return 0;
vector<int> l, r;
for (auto &it : c)
{
if (((it >> idx) & 1) == 0)
l.push_back(it);
else
r.push_back(it);
}
if (!l.size())
return solve(r, idx - 1);
if (!r.size())
return solve(l, idx - 1);
return min(solve(l, idx - 1), solve(r, idx - 1)) + (1 << idx);
}
int main()
{
scanf("%d",&n);
a.resize(n);
for (auto &i : a)
scanf("%d",&i);
printf("%d",solve(a, 30));
return 0;
}
