Leaderboard
Showing:
Handle Score
@Ibrahim Nash 6381
@blackshadows 6329
@mb1973 5388
@Quandray 5231
@akhayrutdinov 5111
@saiujwal13083 4510
@sanjay05 3762
@marius_valentin_dragoi 3522
@sushant_a 3459
@verma_ji 3357
@KshamaGupta 3318
Complete Leaderboard
Total Decoding Messages
Medium Accuracy: 31.27% Submissions: 1388 Points: 4

A top secret message containing letters from A-Z is being encoded to numbers using the following mapping:

'A' -> 1
'B' -> 2
...
'Z' -> 26

You are an FBI agent. You have to determine the total number of ways that message can be decoded.
Note: An empty digit sequence is considered to have one decoding. It may be assumed that the input contains valid digits from 0 to 9 and If there are leading 0’s, extra trailing 0’s and two or more consecutive 0’s then it is an invalid string.

 

Example 1:

Input: str = "123"
Output: 3
Explanation: "123" can be decoded as "ABC"(123),
"LC"(12 3) and "AW"(1 23).

Example 2:

Input: str = "27"
Output: 1
Explanation: "27" can be decoded as "BG".

 

Your Task:
You don't need to read or print anything. Your task is to complete the function CountWays() which takes the string as str as input parameter and returns the total number of ways the string can be decoded modulo 109 + 7.

 

Expected Time Complexity: O(n)
Expected Space Complexity: O(n) where n  = |str|

Constraints:
1 <= |str| <= 104

to report an issue on this page.

Editorial

We strongly recommend solving this problem on your own before viewing its editorial. Do you still want to view the editorial?

Yes

All Submissions

My Submissions:

Login to access your submissions.

Total Decoding Messages

Output Window