Submission #721675

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Source Code Expand

#define _USE_MATH_DEFINES
#include<iostream>
#include<string>
#include<vector>
#include<math.h>
#include<iomanip>
using namespace std;

int main(void) {
	
	signed long long x;
	signed long long y;
	signed long long mi;
	signed long long a = 0;
	signed long long b = 0;
	signed long long c = 1;
	signed long long l = 0;
	signed long long m = 0;
	signed long long d = 0;
	signed long long k = 0;
	signed long long ans = 0;
	vector<long> koko;
	vector<long> yoto;
	cin >> x >> y;
	for (int i = 0; i < x; i++) {
		cin >> b;
		koko.push_back(b);
		yoto.push_back(0);
	}
	if (x / 2 >= y) {
		

		for (int i = y - 1; i <= x - y; i++) {
			a += koko[i];
		}
		for (int i = 0; i < y - 1; i++) {
			b = koko[i] + koko[x - i - 1];
			d += b*c;
			c++;
		}

		signed long long j = a * y + d;
		cout << j << endl;

	}
	else {
		signed long long j = 0;
		for (int i = 0; i < x - y ; i++) {

			yoto[i] = i + 1;
			yoto[x - i - 1] = i + 1;
		}
		for (int i = x-y; i < y; i++) {

			yoto[i] = x-y+1;
			
		}
		for (int i = 0; i < x; i++) {
			l = koko.at(i);
			m = yoto.at(i);
			j += l*m;
		}
		cout << j << endl;
	}
	
	cin >> x;

	
}

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