Encuentra el fin de transferir búsqueda binaria recursiva

búsqueda secuencial

	private static int search(int[] arr, int key) {
		for (int i = 0; i < arr.length; i++) {
			if (arr[i] == key)
				return i;
		}
		return -1;
	}

La solución de búsqueda binaria ordinaria

	private static int binarySearch0(int[] arr, int low, int high, int key) {
		while (low <= high) {
			int mid = low + ((high - low) >> 1);// (low + high) >>>
												// 1;//防止溢出，移位也更高效。同时，每次循环都需要更新。
			int midVal = arr[mid];

			if (midVal < key)
				low = mid + 1;
			else if (midVal > key)
				high = mid - 1;
			else
				return mid; // key found
		}
		return -(low + 1); // key not found.
	}

Búsqueda binaria solución recursiva

public class 二分查找的递归解法 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		int a[] = {1,9,3,6,8,5,8};
		System.out.println(binarySearch(a, 0, 6, 3));
	}
	
	private static int binarySearch(int[] arr, int low, int high, int key){
		if (low > high) {
			return -1;
		}
		
		
		//防止溢出,移位也更高效
		int mid = low + ((high - low)>>1) ;
		int midVal = arr[mid];
		if (midVal < key) {
			return binarySearch(arr, mid + 1, high, key);
		}
		else if (midVal > key) {
			return binarySearch(arr, low, high - 1, key);
		}
		else {
			//key found
			return mid;
		}
	}

}

análisis

全范围内二分查找
    等价于三个子问题：
        左边找（递归）
        中间比
        右边找（递归）
    注意：左查找和右查找只选其一