查找之二分查找

二分查找（java）

public class BinarySearch {
	public static void main(String[] args) {
		int[] a = {1, 2, 3, 4};
		System.out.println(binarySearch(a, 0, a.length - 1, 3));
	}
	public static int binarySearch(int[] array, int low, int high, int target){
		while(high >= low){
			int mid = (low + high) / 2;
			int tmp = array[mid];
			if(tmp < target){
				low = mid + 1;//若array为降序则为high = mid - 1;
			}
			else if(tmp > target)
				high = mid - 1;//若array为降序则为low = mid + 1;
			else 
				return mid;
		}
		return -1;
	}
}