y总找规律+双指针

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 1e5 + 10;
int n;
int a[N];
int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    LL maxs = -1e18;
    int depth = 0;
    for (int d = 1,i = 1; i <= n; i *= 2, d++) {
        LL s = 0;
        for (int j = i; j < i + (1 << d - 1) && j <= n; j++)
            s += a[j];
        if(s>maxs){
            maxs = s;
            depth = d;
        }
    }
    cout << depth << endl;
    return 0;
}

自己写的 根据二叉树的性质标记深度

#include<bits/stdc++.h>
using namespace std;
int n;
const int N = 1e6 + 10;
int a[N];
pair<int, int> tr[N];
long long ans = -0x3f3f3f3f;
int ansdeep = 0;
int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];

    }
    tr[1].second = a[1];
    tr[1].first = 1;
    ans = a[1];
    ansdeep = 1;
    for (int i = 1; i <= n; i++) {
        tr[2 * i].second = a[2 * i];
        tr[2 * i].first = tr[i].first + 1;
        tr[2 * i + 1].second = a[2 * i + 1];
        tr[2 * i + 1].first = tr[i].first + 1;
    }
    sort(tr + 1, tr + n + 1);

    //for (int i = 1; i <= n; i++) {
    //  cout << tr[i].first << ' ' << tr[i].second<<endl;
    //}

    for (int i = 1; i <= n; ) {
        long long sum = 0;
        int nowdeep = tr[i].first;
        while (tr[i].first == nowdeep) {
            sum += tr[i].second;
            i++;
        }
        //cout << sum << ' ';
        if (sum > ans) {
            ansdeep = nowdeep;
        }
        ans = max(ans, sum);
    }
    cout << ansdeep << endl;

    return 0;
}