java 二分查找

package 查找;

public class BinarySearch {

	static int[] itns = new int[]{1,2,3,4,5,6,7,8,9,11,111,323,3443};//必须是有序的才可以
	
	public static void main(String[] args) {
		
		int num = binarySearch(itns,0,itns.length,324); //	递归实现
		
		num = binarySearch_(itns,3443);	//while 实现
		System.out.println(num);
	}
	
	/**  递归
	 * @param ints
	 * @param low
	 * @param high
	 * @param key
	 * @return
	 */
	private static  int binarySearch(int[] ints,int low,int high,int key) {
		if(low>=high){
			return -1;
		}else{
			int midle = (low+high )/2;
			if(ints[midle]==key){
				return midle;
			}
			else if(ints[midle]<key){
				return binarySearch(ints,midle+1,high,key);
			}else{
				return binarySearch(ints,low,midle-1,key);
			}
		}
	}
	
	/**	非递归
	 * @param ints
	 * @param key
	 * @return
	 */
	private static int binarySearch_(int[] ints,int key){
		int midle = ints.length /2;
		int low=0,high=ints.length;
		
		while (low<high) {
			midle = (low+high) / 2;
			if(ints[midle] == key){
				return midle;
			}else if(ints[midle] < key){
				low = midle+1;
			}else if(ints[midle] > key){
				high = midle-1;
			}
		}
		return -1;
	}
	
}