1338A - Powered Addition - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define print(x) cout<<x<<'\n'
#define printe(x) cout<<x<<endl
#define prints(x) cout<<x<<" "
#define rep(i,a,b) for (int i=a;i<b;i++)
#define maxVec(v) *max_element(v.begin(),v.end())
#define minVec(v) *min_element(v.begin(),v.end())
#define bpcnt(a) __builtin_popcount(a)
#define bpcntll(a) __builtin_popcountll(a)
inline ll lsb(ll n) {return n&-n;}
inline ll msb(ll n) {return (1 << (31 - __builtin_clz(n)));}
// bool sortbysec(const pair<ll,ll> &a,
// 			const pair<ll,ll> &b)
// {
// 	return (a.second < b.second);
// }
// Fill whole array with 0.
// memset(arr, 0, n*sizeof(arr[0]));


void solve() {
    int n;
    cin>>n;
    vector<ll> a(n,0);
    rep(i,0,n) cin>>a[i];
    ll maxb = a[0], ans = LLONG_MIN;
    rep(i,1,n) {
        if (a[i]<maxb) {
            ll temp = maxb - a[i] + 1;
            ll ms = 31 - __builtin_clz(temp);
            if (1<<ms == temp) ans = max(ans, ms);
            else ans = max(ans, ms+1);
        }
        maxb = max(maxb,a[i]);
    }
    if (ans == LLONG_MIN) print(0);
    else print(ans);
    return;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int it,t=1;
    cin>>t;
    for (it=0;it<t;it++) {
        solve();
    }
    return 0;
}