洛谷P2512 [HAOI2008]糖果传递

 1 //不开long long见祖宗！！！ 
 2 #include<bits/stdc++.h>
 3 using namespace std;
 4 long long n,ans,sum;
 5 long long a[1000005],s[1000005];
 6 int main()
 7 {
 8     scanf("%lld",&n);
 9     for(int i=1;i<=n;i++) {scanf("%lld",&a[i]);sum+=a[i];}
10     sum/=n;
11     for(int i=1;i<=n;i++) a[i]-=sum;
12     for(int i=1;i<=n;i++) s[i]=s[i-1]+a[i];
13     nth_element(s+1,s+(n+1)/2,s+1+n);//STL根据第n大元素O(n)排序
14     for(int i=1;i<=n;i++) ans+=s[i]>s[(n+1)/2]?s[i]-s[(n+1)/2]:s[(n+1)/2]-s[i];
15     printf("%lld",ans);
16     return 0;
17 }