Niuke practice 101-c reasoning clown - bit operation + thinking

The topic requires a minimum value , According to greedy thought , In the case of binary representation , High position 1 The less, the better.

#include<iostream>
using namespace std;

const int N = 100010;
int a[N];
int res=0;
int main()
{
    
    int n;cin>>n;
    for(int i=1;i<=n;i++)cin>>a[i];
    
    for(int j=30,i;j>=0;j--)// Traverse every bit , Suppose this bit is 0, If the conditions are not met, you must select , by 1
    {
    
        int t=res;
        // Look at number j Position as 0 Whether the conditions are met in the case of 
        for(int k=j-1;k>=0;k--)
        {
    
            t|=1<<k;
            // dissatisfaction break, This must be > Number 
            for(i=1;i<n;i++)if((a[i]&t)>(a[i+1]&t))break;
            // Not satisfied to prove that this person cannot be 1, XOR becomes original value at once 
            if(i!=n)t^=1<<k;
        }
        // Judge whether it is satisfied , Does not meet the requirements of article of the certificate j Bit must be 1
        for(i=1;i<n;i++)if((a[i]&t)>=(a[i+1]&t))break;
        if(i!=n)res|=1<<j;
    }
    cout<<res<<'\n';
}