查找一个数组中第N大的数，并与第一大的数交换

一道算法题：

查找一个数组中第N大的数，并与第一大的数交换

1. 先写一个方法，查找一个数组中第N大的数

/// <summary>

/// While input an int array and an int number n, the method will return the n'th big number in the array

/// </summary>

/// <param name="array">the int array</param>

/// <param name="n">the int number</param>

/// <returns></returns>

public static int FindNumber(int[] array, int n)

{

LinkedList<int> numberLink = new LinkedList<int>();

numberLink.AddFirst(new LinkedListNode<int>(array[0]));

if (array.Length > 1)

{

for (int i = 1; i < array.Length; i++)

{

LinkedListNode<int> currentNode = numberLink.First;

while (currentNode.Value > array[i])

{

if (currentNode == numberLink.Last)

{

numberLink.AddAfter(currentNode, array[i]);

continue;

}

else

{

currentNode = currentNode.Next;

}

}

if (currentNode.Value < array[i])

{

numberLink.AddBefore(currentNode, array[i]);

}

}

}

if (n > numberLink.Count || n < 1)

{

throw new ArgumentOutOfRangeException();

}

LinkedListNode<int> outputNode = numberLink.First;

int count = 1;

while (count < n)

{

outputNode = outputNode.Next;

count++;

}

return outputNode.Value;

}

2. 根据FindNumber方法写出解决该问题方法

public static int[] ReplaceNumber(int[] array,int n)

{

int number = FindNumber(array, n);

int biggestNumber=FindNumber(array,1);

for (int i = 0; i < array.Length; i++)

{

if (array[i] == number)

{

array[i] = biggestNumber;

}

else if (array[i] == biggestNumber)

{

array[i] = number;

}

}

return array;

}