Command Unit Counter

Easy

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Problem statement

You are given a string S which consists only of digits from '1' to '9'. This string can be interpreted as a sequence of commands. A "command unit" can be either:

1) A single digit. 2) A pair of two consecutive digits that form a number less than or equal to 26.

Your task is to count the total number of valid command units (both single-digit and valid two-digit combinations) that can be found in the string.

Detailed explanation ( Input/output format, Notes, Images )

Input Format:

The first line of input contains a single string S.

Output Format:

Print a single integer representing the total count of all valid command units.

Note:

The string S will only contain digits from '1' to '9'.

Every single digit in the string is always considered a valid command unit.

The total count is the sum of all single-digit units plus all valid two-digit units.

Sample Input 1:

Sample Output 1:

Explanation for Sample 1:

The command units are identified as follows:
-Single-digit units:'1', '2', '3'. (Count: 3)
-Two-digit units:
 -'12' forms the number 12. Since 12 <= 26, this is a valid unit.
 -'23' forms the number 23. Since 23 <= 26, this is a valid unit.
-Total valid units = 3 + 2 = 5.

Sample Input 2:

Sample Output 2:

Explanation for Sample 2:

-Single-digit units:'2', '7', '1'. (Count: 3)
-Two-digit units:
 -'27' forms the number 27. Since 27 > 26, this is **not** a valid unit.
 -'71' forms the number 71. Since 71 > 26, this is **not** a valid unit.
-Total valid units = 3 + 0 = 3.

Expected Time Complexity:

The expected time complexity is O(N), where N is the length of the string.

Constraints:

1 <= N <= 10^5
`S` consists only of digits '1' through '9'.

Time limit: 1 sec

Approaches (1)

Approach 1

Command Unit Counter

Time Complexity

The expected time complexity is O(N), where N is the length of the string.

Space Complexity

(100% EXP penalty)

Command Unit Counter

Console