查找之一顺序查找

一、

public class Sequential_SearchDemo01 {
    static int[] num = {1,3,4,6};
    public static void main(String[] args) {
        int key = 7;
        boolean x = Sequential_Search(key);
        System.out.println(x);
    }
    private static boolean Sequential_Search(int key) {
        for(int i=0;i<num.length;i++){
            if(num[i] == key){
                return true;
            }
        }
        return false;
    }
}

输出结果为：false

二、顺序查找的优化

public class Sequential_SearchDemo02 {
    static int[] num = {0,5,8,9,6,3};
    public static void main(String[] args) {
        int key = 7;
        int x = Sequential_Search(key);
        System.out.println(x);
    }
    private static int Sequential_Search(int key) {
        int i;
        num[0] = key;
        i = num.length - 1;
        while(num[i] != key){
            i--;
        }
        return i;
    }

}

如果输出为0，表示没有查到key，；

时间复杂度为O(n)