【数据结构与算法】二分查找

最近看MySQL索引原理，得知在InnnoDB引擎下其数据结构为B+树，而B+树每个节点上有多个key，当查找某个key时使用二分查找。所以，付下下二分查找吧~

前提：查找的数组本身应是有序的。
过程：

public class BinarySearch {

    public static void main(String[] args) {
		int[] values = {1, 3, 4, 5, 6, 9, 10, 34, 99};
		System.out.println(binarySearch(values, 1));
		System.out.println(binarySearch(values, 2));
		System.out.println(binarySearch(values, 3));
		System.out.println(binarySearch(values, 5));
		System.out.println(binarySearch(values, 34));
		System.out.println(binarySearch(values, 99));
	}
	
	public static int binarySearch(int[] values, int target) {
		if (values == null || values.length == 0) {
			return -1;
		}
		
		int startIndex = 0;
		int endIndex = values.length - 1;
		int middleIndex = 0;
		while (startIndex <= endIndex) {
			middleIndex = (startIndex + endIndex) / 2;
			
			if (values[middleIndex] == target) {
				return middleIndex;
			} else if (values[middleIndex] < target) {
				startIndex = middleIndex + 1;
			} else if (values[middleIndex] > target) {
				endIndex = middleIndex - 1;
			}
		}
		
		return -1;
	}

}