一个数组[1,2,3,4,6,8,9,4,8,11,18,19,100] 前半部分是是一个递增数组，后面一个还是递增数组，但整个数组不是递增数组，那么怎么最快的找出其中一个数？

int binaryFind(int* arr, int low, int high, int target) {
	while (low <= high) {
		int middle = (low + high) >> 1;    //(low+high)/2
		if (arr[middle] == target)
			return middle;
		//在右半边
		else if (arr[middle] < target)
			low = middle + 1;
		//在左半边
		else
			high = middle - 1;
	}
	return -1;
}

int find(int* arr, int len, int target) {
	int nextBegin = -1;
	for (int i = 1; i < len; ++i) {
		if (arr[i - 1] > arr[i]) {	//找到分界点
			nextBegin = i;
			break;
		} else if (arr[i] == target) {	//找到分界点前找到目标
			return i;
		}
	}

	//后半部分使用二分查找
	if (nextBegin != -1) {
		return binaryFind(arr, nextBegin, len - 1, target);
	}
	return -1;
}