二分法查找数据

二分法查找数据前提：数组必须是有序数组

图示：

代码：

public class BinarySearchTest {
	public int binarySearch(int[] arr,int value){
		int middleA = 0;
		int leftA = 0;
		int rightA = arr.length - 1;

		while (true) {
			middleA = ((rightA + leftA) / 2);
			if (arr[middleA] == value) {
				return middleA;
			}else if(leftA > rightA){
				return -1;
			}else {
				if(arr[middleA] > value){
					rightA = middleA - 1;
				}else {
					leftA = middleA + 1;
				}
			}
		}
	}
	public static void main(String[] args) {
			int[] arr = new int[]{1,3,4,6,8,9,10,38,50};
			BinarySearchTest bst = new BinarySearchTest();
			System.out.println(bst.binarySearch(arr,4));
			}
}