Java二分法查找

二分法查找

     /**
     * 二分法查找 找不到返回-1
     * @author yangzi
     *
     */
     public class TwoFind {

	     public static int twoFind(int ia, int[] arr, int left, int right) {

            if (left > right) {
		return -1;
	}
	if (arr[(left + right) / 2] == ia) {
		return (left + right) / 2;
	}
	if (arr[(left + right) / 2] < ia) {
		return twoFind(ia, arr, (left + right) / 2 + 1, right);
	}
	if (arr[(left + right) / 2] > ia) {
		return twoFind(ia, arr, left, (left + right) / 2 - 1);
	}
	return -1;

    }

    public static void main(String[] args) {
	// 		下标	  0                    7  8                          15
	int[] arr = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
	int ia = 16;
	int left = 0;
	int right = arr.length - 1;
	// 调用
	System.out.println(twoFind(ia, arr, left, right));
    }

}