数组拷贝，二分法查找

Arrays.copyOfRange(int[] arr,int开始下标，int结束下标)//左闭右开
System.arraycopy（int[] source,int开始下标，int[] dest,int开始下标，int拷贝多少个）

这里是手动拷贝：
public static int[] copyOf(int[] original, int newLength) {
	int[] dest = new int[newLength];
	int length = original.length <= newLength ? original.length : newLength;
	for (int i = 0; i < length; i++) {
		dest[i] = original[i];
	}
	
	return dest;
}



mid作为分水岭，  不断地缩小范围
// 前提需要数组是有序的
public static int binarySearch(int[] a, int v) {
	int left = 0;
	int right = a.length;
	
	while (left < right) {
		int mid = (left + right) / 2;
		if (v == a[mid]) {
			return mid;
		} else if (v < a[mid]) {
			right = mid;
		} else {
			left = mid + 1;
		}
	}
	
	return -1;
}


public static int binarySearch2(int[] a, int v) {
	int left = 0;
	int right = a.length - 1;
	
	while (left <= right) {
		int mid = (left + right) / 2;
		if (v == a[mid]) {
			return mid;
		} else if (v < a[mid]) {
			right = mid - 1;
		} else {
			left = mid + 1;
		}
	}
	
	return -1;
}