Problem Statement

You are given an integer sequence of length?N,?a=?{a₁,a₂,…,a_N}, and an integer?K.

a?has?N(N+1)?2?non-empty contiguous subsequences, {a_l,a_l+1,…,a_r}?(1≤l≤r≤N). Among them, how many have an arithmetic mean that is greater than or equal to?K?

Constraints

• All input values are integers.
• 1≤N≤2×10⁵
• 1≤K≤10⁹
• 1≤a_i≤10⁹

Input

Input is given from Standard Input in the following format:

N K a₁ a₂ : a_N

Output

Print the number of the non-empty contiguous subsequences with an arithmetic mean that is greater than or equal to?K.

Sample Input 1

3 6 7 5 7

Sample Output 1

5

All the non-empty contiguous subsequences of?a?are listed below:

• {a₁} = {7}
• {a₁,a₂} = {7,5}
• {a₁,a₂,a₃} = {7,5,7}
• {a₂} = {5}
• {a₂,a₃} = {5,7}
• {a₃} = {7}

Their means are?7,?6,?19?3,?5,?6?and?7, respectively, and five among them are?6or greater. Note that {a₁} and {a₃} are indistinguishable by the values of their elements, but we count them individually.

Sample Input 2

1 2 1

Sample Output 2

0

Sample Input 3

7 26 10 20 30 40 30 20 10

Sample Output 3

13


樹狀數組sb題。

#include<bits/stdc++.h> #define ll long long using namespace std; const int maxn=200005; ll num[maxn],a[maxn],ans; int n,r[maxn],f[maxn],k,ky; inline int read(){int x=0; char ch=getchar();for(;!isdigit(ch);ch=getchar());for(;isdigit(ch);ch=getchar()) x=x*10+ch-'0';return x; } inline void update(int x,int y){ for(;x<=ky;x+=x&-x) f[x]+=y;} inline int query(int x){ int an=0; for(;x;x-=x&-x) an+=f[x]; return an;} int main(){scanf("%d%d",&n,&k);for(int i=1;i<=n;i++) a[i]=read()-k;for(int i=1;i<=n;i++){a[i]+=a[i-1],num[i]=a[i];if(a[i]>=0) ans++;}sort(num+1,num+n+1);ky=unique(num+1,num+n+1)-num-1;for(int i=1;i<=n;i++) r[i]=lower_bound(num+1,num+ky+1,a[i])-num;for(int i=1;i<=n;i++) ans+=(ll)query(r[i]),update(r[i],1);printf("%lld\n",ans);return 0; }

　　

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轉載于:https://www.cnblogs.com/JYYHH/p/8921882.html

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