[セットトップ]二分検索ターゲット要素インデックス

package com.zhangry.search;

public class BinarySearch {

    public static void main(String[] args) {
        int[] arrayForSearch = {1,2,3,4,5,6,7,8,9,10};
        int start = 0;
        int end = arrayForSearch.length-1;
        int target = 3;
        System.out.println(target+"         : "+binarySearch(arrayForSearch,start,end,target));
    }
    
    private static int binarySearch(int[] arrayForSearch,int start,int end,int target){
        int current = (start+end)/2;
        if(arrayForSearch[current] == target){
            return current;
        }else if(arrayForSearch[current] > target){
            end =  current;
            return binarySearch(arrayForSearch,start,end,target);
        }else if(arrayForSearch[current] < target){
            start = current;
            return binarySearch(arrayForSearch,start,end,target);
        }
        return -1;
    }

}

 
 

package com.zhangry.search;

public class WhileBinarySearch {
    /**
     *       
     * @param srcArray　     
     * @param des　     *
     * @return des     ，     -1
     */
    public static int binarySearch(int[] srcArray, int des) {
        int low = 0;
        int high = srcArray.length - 1;
        while (low <= high) {
            int middle = (low + high) / 2;
            if (des == srcArray[middle]) {
                return middle;
            } else if (des < srcArray[middle]) {
                high = middle - 1;
            } else {
                low = middle + 1;
            }
        }
        return -1;
    }

    public static void main(String[] args) {
        int[] src = new int[] { 1, 3, 5, 7, 8, 9 };
        System.out.println(binarySearch(src, 8));
    }
}