Define an array to be a 121 array if all elements are either 1 or 2 and it begins with one or more 1s followed by a one or more 2s and then ends with the same number of 1s that it begins with. Write a method named is121Array that returns 1 if its array argument is a 121 array, otherwise, it returns 0. There is one additional requirement. You should return 0 as soon as it is known that the array is not a 121 array; continuing to analyze the array would be a waste of CPU cycles. If you are programming in Java or C#, the function signature is int is121Array(int[ ] a) If you are programming in C or C++, the function signature is int is121Array(int a[ ], int len) where len is the number of elements in the array a. Examples
Define an array to be a 121 array if all elements are either 1 or 2 and it begins with one or more 1s followed by a one or more 2s and then ends with the same number of 1s that it begins with. Write a method named is121Array that returns 1 if its array argument is a 121 array, otherwise, it returns 0.
There is one additional requirement. You should return 0 as soon as it is known that the array is not a 121 array; continuing to analyze the array would be a waste of CPU cycles.
If you are
int is121Array(int[ ] a)
If you are programming in C or C++, the function signature is
int is121Array(int a[ ], int len) where len is the number of elements in the array a.
Examples
|
a is |
then function returns |
reason |
|
{1, 2, 1} |
1 |
because the same number of 1s are at the beginning and end of the array and there is at least one 2 in between them. |
|
{1, 1, 2, 2, 2, 1, 1} |
1 |
because the same number of 1s are at the beginning and end of the array and there is at least one 2 in between them. |
|
{1, 1, 2, 2, 2, 1, 1, 1} |
0 |
Because the number of 1s at the end does not equal the number of 1s at the beginning. |
|
{1, 1, 2, 1, 2, 1, 1} |
0 |
Because the middle does not contain only 2s. |
|
{1, 1, 1, 2, 2, 2, 1, 1, 1, 3} |
0 |
Because the array contains a number other than 1 and 2. |
|
{1, 1, 1, 1, 1, 1} |
0 |
Because the array does not contain any 2s |
|
{2, 2, 2, 1, 1, 1, 2, 2, 2, 1, 1} |
0 |
Because the first element of the array is not a 1. |
|
{1, 1, 1, 2, 2, 2, 1, 1, 2, 2} |
0 |
Because the last element of the array is not a 1. |
|
{2, 2, 2} |
0 |
Because there are no 1s in the array. |
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