मैं बाइनरी सर्च नहीं लिख सकता

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

for (int i = 0; i <= array.Length - 1; i++)

static int BinarySearch_Rec_Wrapper(int[] array, int element)
{
    BinarySearch_Rec(array, element, 0, array.Length);
}

int mid = (left + right) / 2 

 int mid = left + (right - left) / 2

:

static int BinarySearch_Rec(int[] array, int key, int left, int right)
{
    int mid = left + (right - left) / 2;

    if (array[mid] == key)
        return mid;

    else if (array[mid] > key)
        return BinarySearch_Rec(array, key, left, mid);
    else
        return BinarySearch_Rec(array, key, mid + 1, right);
}

:

static int BinarySearch_Iter(int[] array, int key)
{
    int left = 0;
    int right = array.Length;

    while (true)
    {
        int mid = left + (right - left) / 2;

        if (array[mid] == key)
            return mid;

        if (array[mid] > key)
            right = mid;
        else
            left = mid + 1;
    }
}

:

:

static int BinarySearch_Rec(int[] array, int key, int left, int right)
{
    int mid = left + (right - left) / 2;

    if (left >= right)
        return -(1 + left);

    if (array[mid] == key)
        return mid;

    else if (array[mid] > key)
        return BinarySearch_Rec(array, key, left, mid);
    else
        return BinarySearch_Rec(array, key, mid + 1, right);
}

:

static int BinarySearch_Iter(int[] array, int key)
{
    int left = 0;
    int right = array.Length;
    int mid = 0;

    while (!(left >= right))
    {
        mid = left + (right - left) / 2;

        if (array[mid] == key)
            return mid;

        if (array[mid] > key)
            right = mid;
        else
            left = mid + 1;
    }

    return -(1 + left);
}

:

№3

:

static int BinarySearch_Rec(int[] array, bool descendingOrder, int key, int left, int right)
{
    int mid = left + (right - left) / 2;

    if (left >= right)
        return -(1 + left);

    if (array[mid] == key)
        return mid;

    else if ((array[mid] > key) ^ descendingOrder)
        return BinarySearch_Rec(array, descendingOrder, key, left, mid);
    else
        return BinarySearch_Rec(array, descendingOrder, key, mid + 1, right);
}

static int BinarySearch_Rec_Wrapper(int[] array, int key)
{
	if (array.Length == 0)
        return -1;

    bool descendingOrder = array[0] > array[array.Length - 1];
    return BinarySearch_Rec(array, descendingOrder, key, 0, array.Length);
}

:

static int BinarySearch_Iter(int[] array, bool descendingOrder, int key)
{
    int left = 0;
    int right = array.Length;
    int mid = 0;

    while (!(left >= right))
    {
        mid = left + (right - left) / 2;

        if (array[mid] == key)
            return mid;

        if ((array[mid] > key) ^ descendingOrder)
            right = mid;
        else
            left = mid + 1;
    }

    return -(1 + left);
}

static int BinarySearch_Iter_Wrapper(int[] array, int key)
{
	if (array.Length == 0)
    	return -1;

    bool descendingOrder = array[0] > array[array.Length - 1];
    return BinarySearch_Iter(array, descendingOrder, key);
}

:

№4

:

static int BinarySearch_Rec(int[] array, bool descendingOrder, int key, int left, int right)
{
    int mid = left + (right - left) / 2;

    if (left >= right)
        return -(1 + left);

    if (array[left] == key)
        return left;

    if (array[mid] == key)
    {
        if (mid == left + 1)
            return mid;
        else
            return BinarySearch_Rec(array, descendingOrder, key, left, mid + 1);
    }

    else if ((array[mid] > key) ^ descendingOrder)
        return BinarySearch_Rec(array, descendingOrder, key, left, mid);
    else
        return BinarySearch_Rec(array, descendingOrder, key, mid + 1, right);
}

static int BinarySearch_Rec_Wrapper(int[] array, int key)
{
    if (array.Length == 0)
        return -1;

    bool descendingOrder = array[0] > array[array.Length - 1];
    return BinarySearch_Rec(array, descendingOrder, key, 0, array.Length);
}

:

static int BinarySearch_Iter(int[] array, bool descendingOrder, int key)
{
    int left = 0;
    int right = array.Length;
    int mid = 0;

    while (!(left >= right))
    {
        mid = left + (right - left) / 2;

        if (array[left] == key)
            return left;

        if (array[mid] == key)
        {
            if (mid == left + 1)
                return mid;
            else
                right = mid + 1;
        }

        else if ((array[mid] > key) ^ descendingOrder)
            right = mid;
        else
            left = mid + 1;
    }

    return -(1 + left);
}

static int BinarySearch_Iter_Wrapper(int[] array, int key)
{
    if (array.Length == 0)
        return -1;

    bool descendingOrder = array[0] > array[array.Length - 1];
    return BinarySearch_Iter(array, descendingOrder, key);
}

№5

enum ElementToChoose
{
	First,
	Last,
	NoCare
}

/// <summary>
/// Finds element equal to value in sorted array in range [low, high)
/// </summary>
static int binarySearch(int value, int[] array, bool ascendingOrder, ElementToChoose elementToChoose, int low, int high) {
	// return valid invalid position
	if (low >= high)
		return -(low + 1);

	// return first or last found element
	if (elementToChoose == ElementToChoose.First)
		if (value == array[low])
			return low;

	int last = high - 1;

	if (elementToChoose == ElementToChoose.Last)
		if (value == array[last])
			return last;

	int mid = low + (high - low) / 2;

	// we have found some element
	if (value == array[mid]) {
		switch (elementToChoose) {
			case ElementToChoose.NoCare:
				return mid;

			case ElementToChoose.First:
				if (mid - low <= 1)
					// array[mid] is the earliest element in array, return it
					// because array[low] != value && array[low+1] == value, where mid == low + 1
					return mid;
				else
					// try to find first element
					// don't forget to capture current element {|0, 0|, 1} -> {0, 0}
					return binarySearch(value, array, ascendingOrder, elementToChoose, low, mid + 1);
			case ElementToChoose.Last:
				if (last - mid <= 1)
					// array[mid] is the last element in array, return it
					// because array[last] != value && array[last - 1] == value, where mid == last - 1
					return mid;
				else
					// try to find last element
					// don't forget to capture current element {0, |0, 1|} -> {0, 1}
					return binarySearch(value, array, ascendingOrder, elementToChoose, mid, high);
		}
	}

	// choose left or right half, depending on sorting order & comparing value and mid
	if ((value < array[mid]) ^ !ascendingOrder)
		return binarySearch(value, array, ascendingOrder, elementToChoose, low, mid);
	else
		return binarySearch(value, array, ascendingOrder, elementToChoose, mid + 1, high);
}

//   - Func<float, float> ,  float   float
static float BinarySearch_Func(Func<float, float> func, bool descendingOrder, float key, float left, float right)
{
    float mid = (left + right) / 2;

    if (left == mid || mid == right)
        return mid;

    if ((func(mid) > key) ^ descendingOrder)
        return BinarySearch_Func(func, descendingOrder, key, left, mid);
    else
        return BinarySearch_Func(func, descendingOrder, key, mid, right);
}

static float BinarySearch_Func_Wrapper(Func<float, float> func, float key, float left, float right)
{
    if (left > right)
        return float.NaN;

    bool descendingOrder = func(left) > func(right);
    bool isOk = true;

    if (!descendingOrder)
        isOk = func(left) <= key && key <= func(right);
    else
        isOk = func(right) <= key && key <= func(left);

    if (isOk)
        return BinarySearch_Func(func, descendingOrder, key, left, right);
    else
        return float.NaN;
}

//   x => x - -  f(x) = x
Console.WriteLine(BinarySearch_Func_Wrapper(x => x, 0.7f, 0.7f, 100.0f)); // : 0.7
Console.WriteLine(BinarySearch_Func_Wrapper(x => x, 0.8f, 0.8f, 100.0f)); // : 0,8000001
Console.WriteLine(BinarySearch_Func_Wrapper(x => x, 0.9f, 0.9f, 100.0f)); // : 0,9

Console.WriteLine("{0:0.00000000}",0.8f); // : 0,80000000