查找之一顺序查找

一、

 1 public class Sequential_SearchDemo01 {
 2     static int[] num = {1,3,4,6};
 3     public static void main(String[] args) {
 4         int key = 7;
 5         boolean x = Sequential_Search(key);
 6         System.out.println(x);
 7     }
 8     private static boolean Sequential_Search(int key) {
 9         for(int i=0;i<num.length;i++){
10             if(num[i] == key){
11                 return true;
12             }
13         }
14         return false;
15     }
16 }

输出结果为：false

二、顺序查找的优化

 1 public class Sequential_SearchDemo02 {
 2     static int[] num = {0,5,8,9,6,3};
 3     public static void main(String[] args) {
 4         int key = 7;
 5         int x = Sequential_Search(key);
 6         System.out.println(x);
 7     }
 8     private static int Sequential_Search(int key) {
 9         int i;
10         num[0] = key;
11         i = num.length - 1;
12         while(num[i] != key){
13             i--;
14         }
15         return i;
16     }
17
18 }

如果输出为0，表示没有查到key，；

时间复杂度为O(n)