二分查找法 日记

package test;

import java.util.Arrays;

public class DichotomyTest {

    public static void main(String[] args) {
        // System.out.println(Sorting(getArray(), 88));
        System.out.println(Sorting(getArray(), 0, getArray().length - 1, 3));
    }

    public static int[] getArray() {
        int[] array = new int[10];
        array[0] = 10;
        array[1] = 15;
        array[2] = 10;
        array[3] = 22;
        array[4] = 18;
        array[5] = 51;
        array[6] = 4;
        array[7] = 21;
        array[8] = 88;
        array[9] = 3;
        Arrays.sort(array);
        return array;
    }

    // 二分查找法（非递归）
    public static int Sorting(int[] array, int code) {
        int len = array.length;
        int start = 0, end = len - 1, mid;
        while (start <= end) {
            mid = (end + start) / 2;// 中间数会渐渐接近指定数
            if (code == 0 || array.length ==0 ) {
                return -1;
            }
            if (array[mid] == code) {
                return mid;
            } else if (array[mid] < code) {
                start = mid + 1;
            } else {
                end = mid - 1;
            }
        }
        return -1;
    }

    // 递归查找
    public static int Sorting(int[] array, int start, int end, int code) {

        int mid = (start + end) / 2;
        if (code == 0 || array.length ==0 || start>end) {
            return -1;
        }
        if (array[mid] == code) {
            return mid;
        } else if (array[mid] < code) {
            return Sorting(array, mid + 1, end, code);
        } else {
            return Sorting(array, start, end - 1, code);
        }

    }
}