求解非递减数组范围下标

题目

有序非递减数组，找出在指定区间中的元素位置，输出起始和结束位置的下标。
如数组： 1,2,2,3,4,6
区间:2,8(大于等于2，小于等于8)
结果1,5（1是符合区间最左边的下标，5是符合区间最右边的下标）
要求时间复杂度要小于O(N)(不可以是O(N))

解法1:二分查找

private int[] array = {1,2,2,3,4,6};

private int min = -20;

private int max = 8;

public void binarySearch() {
	int left = binarySearch(array,min,true);
	int right = binarySearch(array,max,false);
	System.out.println(left +" "+ right);
}

private int binarySearch(int[] array,int target,boolean first){
	int length = array.length;
	if (length == 0) {
		return -1;
	}
	if (array[0] > max) {
		return -1;
	}
	if (array[length-1] < min) {
		return -1;
	}
	int left = 0,right = length -1;
	while (left <= right) {
		int mid = left + (right -left)/2;
		if (array[mid] > target) {
			right = mid - 1;
		}else if (array[mid] < target) {
			left = mid + 1;
		}else {
			if (first) {
				if (mid == 0 || array[mid - 1] != target) {
					return mid;
				} else {
					right = mid - 1;
				}
			} else {
				if (mid == 0 || array[mid + 1] != target) {
					return mid;
				} else {
					left = mid + 1;
				}
			}
		}
	}
	if (first) {
		return left;
	} else {
		return right;
	}
}

github源码