【单调队列】合并果子

#include <bits/stdc++.h>
#define ll long long
#define met(a) memset(a,0,sizeof(a))
#define inf 0x3f3f3f3f
using namespace std;
const int mod=1e9+7;
int a[10010];
int main()
{
    int i,j,k,m,n;
    cin>>n;
    for (i = 1; i <=n; i++)
        cin >> a[i];
    sort(a+1,a+n+1);
    int st = 1, ed = n+1, st1 = 0, ed1 = 0;
    ll ans=0,cnt;
    while (1)
    {
        cnt=0;
        if (st == ed&&st1 + 1 == ed1)
            break;
        for (j =1; j <=2; j++)
        {
            if (st != ed)
            {
                if (st1 != ed1)
                    if(a[st]<a[st1])
                    {
                        cnt+=a[st];
                        st++;
                    }
                    else
                    {
                        cnt+=a[st1];
                        st1++;
                    }
                else
                {
                    cnt+= a[st];
                    st++;
                }
            }
            else
            {
                cnt += a[st1];
                st1++;
            }
        }
        ans += cnt;
        a[ed1++] = cnt;
    }
    cout << ans<< endl;
    return 0;
}