二分查找递归与非递归式实现

递归式：

    /**
     * 递归式二分查找实现
     * @param arr
     * @param left
     * @param right
     * @param value
     * @return
     */
    public static int binarySearch1(int[] arr, int left, int right, int value){
        if (left > right) return -1;
        int mid = (left + right) >> 1;
        int midVal = arr[mid];
        if (midVal > value) {
            return binarySearch1(arr,0,mid-1,value);
        }else if (midVal < value){
            return binarySearch1(arr,mid + 1,right,value);
        }else if (midVal == value){
            return mid;
        }
        return -1;
    }

非递归式：

    /**
     * 非递归式二分查找实现
     * @param arr
     * @param target
     * @return
     */
    public static int binarySearch2(int[] arr, int target){
        int left = 0;
        int right = arr.length - 1;

        while (left <= right){//条件满足继续查找
            int mid = (left + right) >> 1;
            if (arr[mid] == target){
                return mid;
            }else if (arr[mid] > target){
                right = mid - 1;//需要向左查找，调整right
            }else if (arr[mid] < target){
                left = mid + 1;//需要向右查找，调整left
            }
        }
        return -1;
    }