二分法的递归与非递归写法

 

public class Test {
	public static void main(String[] args) {
		System.out.println(binarySearchNonRecursive(new int[] {1,4,5,7}, 5));
	}
	// 二分查找递归
	public static int binarySearchRecursive(int[] arr, int num, int start, int end) {
		if (start > end)
			return -1;
		int mid = start + ((end - start) >> 1);
		if (arr[mid] == num)
			return mid;
		else if (arr[mid] < num)
			return binarySearchRecursive(arr, num, mid + 1, end);
		else
			return binarySearchRecursive(arr, num, start, mid - 1);
	}

	// 二分查找非递归
	public static int binarySearchNonRecursive(int[] arr, int num) {
		int left = 0, right = arr.length - 1;
		while (left <= right) {
			int mid = left + ((right - left) >> 1);
			if(arr[mid]==num)return mid;
			else if(arr[mid]<num)
				left=mid+1;
			else right=mid-1;
		}
		return -1;
	}
}