折半查找

基本原理：每次查找都对半分，但要求数组是有序的

public class Solution {

    public static int BinarySearch(int[] sz,int key){
        int low = 0;
        int high = sz.length - 1;
        
        while (low <= high) {
            int middle = (low + high) / 2;
            if(sz[middle] == key){
                return middle;
            }else if(sz[middle] > key){
                high = middle - 1;
            }else {
                low = middle + 1;
            }
        }
        return -1;
    }
}