牛客练习赛7 E 珂朵莉的数列（树状数组+爆long long解决方法）

https://www.nowcoder.com/acm/contest/38/E

题意：

思路：

树状数组维护。从大佬那里学习了如何处理爆long long的方法。

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;
 typedef long long ll;
 const int maxn = +;

 int n;
 int a[maxn],b[maxn];
 ll c[maxn];

 int lowbit(int x)
 {
     return x&(-x);
 }

 void add(int x ,int d)
 {
     while(x<maxn)
     {
         c[x] += d;
         x += lowbit(x);
     }
 }

 ll sum(int x)
 {
     ll ret = ;
     while(x>)
     {
         ret += c[x];
         x -= lowbit(x);
     }
     return ret;
 }

 int main()
 {
     //freopen("in.txt","r",stdin);
     scanf("%d",&n);
     for(int i=;i<=n;i++)
     {
         scanf("%d",&a[i]);
         b[i] = a[i];
     }
     sort(b+,b+n+);
     int num = unique(b+,b+n+)-(b+);
     ll ans1 = , ans2 = ;
     ll mx = 1e18;
     for(int i=;i<=n;i++)
     {
         a[i] = lower_bound(b+,b+n+,a[i])-(b+);
         a[i]++;
         ans1 += (ll)(n-i+)*(sum(n)-sum(a[i]));
         if(ans1>=mx)  ans2 += ans1/mx, ans1%=mx;
         add(a[i],i);
     }
     if(ans2)  printf("%lld%018lld\n",ans2,ans1);
     else printf("%lld\n",ans1);
     return ;
 }