Homework 2

Posted 2020-06-20

题目一代码：

1. public intfindLast(int[] x, inty) {
2. //Effects: If x==null throw
3. NullPointerException
4. // else return the index of the last element
5. // in x that equals y.
6. // If no such element exists, return -1
7. for (inti=x.length-1; i> 0; i--)
8. {
9. if (x[i] == y)
10. {
11. return i;
12. }
13. }
14. return -1;
15. }
16. // test: x=[2, 3, 5]; y = 2
17. // Expected = 0

1、第七行i>0,使得数组缺少第一个元素，应该改为i>=0

2、x = []；

3、x = [2,3,4] y=3;

4、x = [1,2,0] y=3;

题目二代码：

1. public static intlastZero(int[] x) {
2. //Effects: if x==null throw
3. NullPointerException
4. // else return the index of the LAST 0 in x.
5. // Return -1 if 0 does not occur in x
6. for (inti= 0; i< x.length; i++)
7. {
8. if (x[i] == 0)
9. {
10. return i;
11. }
12. } return -1;
13. }
14. // test: x=[0, 1, 0]
15. // Expected = 2

1、第六行，查找最后一个应该从数组最后一位查找for(int i=x.length-1;i>=0;i--)；

2、x = []；

3、x = [2,3,4]；

4、x = [1,2,0]；