Sorted array, given a key, find its left most index or right most index in array. If it isn't in array, return -1.

BinarySearchOfLeftOrRightBoundary.java

public static int findLeftMostElement(int[] A, int key){
    if (A.length == 0) return -1;
    int low = 0, high = A.length-1;
    while (low < high-1){
        int mid = low + (high - low)/2;
        if (A[mid] < key)
            low = mid;
        else
            high = mid;
    }    
    if (A[low] == key)
        return low;
    if (A[high] == key)
        return high;
    return -1;
}
// Using standard binary search template
public static int findLeftMostElement(int[] A, int key){
	if (A.length == 0) return -1;
	int low = 0, high = A.length-1;
	while (low <= high){
		int mid = low + (high - low)/2;
		if (A[mid] == key && (mid == 0 || A[mid-1] < key))
			return mid;
		else if (A[mid] < key)
			low = mid + 1;
		else
			high = mid - 1;
	}
	return -1;
}

public static int findRightMostElement(int[] A, int key){
	if (A.length == 0) return -1;
	int low = 0, high = A.length-1;
	while (low < high-1){
		int mid = low + (high - low)/2;
		if (A[mid] <= key)
			low = mid;
		else
			high = mid;
	}
	if (A[high] == key)
		return high;
	if (A[low] == key)
		return low;
	return -1;
}
// Using standard binary search template
public static int findRightMostElement(int[] A, int key){
	if (A.length == 0) return -1;
	int low = 0, high = A.length-1;
	while (low <= high){
		int mid = low + (high - low)/2;
		if (A[mid] == key && (mid == A.length-1 || A[mid+1] > key))
			return mid;
		else if (A[mid] <= key)
			low = mid + 1;
		else
			high = mid - 1;
	}
	return -1;
}