Caddi Programming Contest 2021(AtCoder Beginner Contest 193) ----- C（思维)_given is a number sequence aa of length nn. find t

 

C - Squared Error 

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Time Limit: 2 sec / Memory Limit: 1024 MB

Score : 300300 points

Problem Statement

Given is a number sequence AA of length NN.
Find the sum of squared differences of every pair of elements: N∑i=2i−1∑j=1(Ai−Aj)2∑i=2N∑j=1i−1(Ai−Aj)2.

Constraints

• 2≤N≤3×1052≤N≤3×105
• |Ai|≤200|Ai|≤200
• All values in input are integers.

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Input

Input is given from Standard Input in the following format:

NN
A1A1 A2A2 A3A3 ⋯⋯ ANAN

Output

Print the answer.

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Sample Input 1 Copy

Copy

3
2 8 4

Sample Output 1 Copy

Copy

56

We have ∑Ni=2∑i−1j=1(Ai−Aj)2=(8−2)2+(4−2)2+(4−8)2=56∑i=2N∑j=1i−1(Ai−Aj)2=(8−2)2+(4−2)2+(4−8)2=56.

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Sample Input 2 Copy

Copy

5
-5 8 9 -4 -3

Sample Output 2 Copy

Copy

950

 

 

题解：
 

code:
 

#include<bits/stdc++.h>
#define INF 0x3f3f3f3f
#define N 100003
#define mod 100000
#define pb push_back
#define x first
#define y second
#define ull unsigned long long
#define ll long long
using namespace std;
set<ll>s;
int main()
{
	
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
	ll n;
	cin >> n;
	for(ll i = 2;i * i <= n;i++)
	{
		for(ll j = 2;;j++)
		{
			ll tmp = pow(i,j);
			if(tmp <= n)
			s.insert(tmp);
			else
			break;
		}
	}
	cout << n - s.size() << endl; 
    return 0;
}