Hackerrank - Game Of Rotation 题解

旋转一个数组以得到最大值。

陷阱就是：不能排序。须要模拟操作旋转，并设计公式计算旋转后的和。

要求是O(n)时间完毕。

原题：

https://www.hackerrank.com/challenges/game-of-rotation

#pragma once
#include <stdio.h>

class GameOfRotation
{
public:
	GameOfRotation()
	{
		int N = 0;
		scanf("%d", &N);
		int *A = new int[N];
		long long one = 0, sum = 0, ans = 0;
		for (int i = 0; i < N; i++)
		{
			scanf("%d", &A[i]);
			one += (long long)A[i];
			sum += (long long)(i+1) * (long long)A[i];
		}
		ans = sum;
		for (int i = 1; i < N; i++)
		{
			sum = sum - one + (long long)A[i-1] * (long long)N;
			ans = ans < sum ? sum : ans;
		}
		printf("%lld", ans);
		delete [] A;
	}
};

int gameOfRotation()
{
	GameOfRotation();
	return 0;
}