回文数组 参考代码

#include <bits/stdc++.h>
using namespace std;

typedef long long LL;
const int maxn = 100000 + 100;
int n;
LL ans;
int num[maxn];

int main() {
#ifdef ExRoc
    freopen("test.txt", "r", stdin);
#endif
    ios::sync_with_stdio(false);

    cin >> n;
    for (int i = 1; i <= n; ++i) {
        cin >> num[i];
    }
    for (int i = 1; i <= n / 2; ++i) {
        int d = num[n - i + 1] - num[i];
        ans += abs(d);
        num[i] += d;
        if (d > 0) {
            num[i + 1] += min(max(num[n - i] - num[i + 1], 0), d);
        }
        if (d < 0) {
            num[i + 1] += max(min(num[n - i] - num[i + 1], 0), d);
        }
    }
    cout << ans << endl;

    return 0;
}