Missing Number in Concatenated Sequence

You were given a sequence of consecutive nonnegative integers but missed one while appending them to create a string S. Your task is to identify the missing integer from this sequence.

If it is possible to form a sequence of consecutive integers by identifying the missing integer, then return that number. If the string is incorrectly formed with more than one missing integer, no missing integer, or the string is invalid, return -1.

Example:

Input:

T = 1
S = "1113"

Output:

12

Explanation:

The sequence was 11, 12, 13, but 12 was missed, leading to the string "1113".

Constraints:

1

Question

Missing Number in Concatenated Sequence

You were given a sequence of consecutive nonnegative integers but missed one while appending them to create a string S. Your task is to identify the missing integer from this sequence.

If it is possible to form a sequence of consecutive integers by identifying the missing integer, then return that number. If the string is incorrectly formed with more than one missing integer, no missing integer, or the string is invalid, return -1.

Example:

Input:

T = 1
S = "1113"

Output:

Explanation:

The sequence was 11, 12, 13, but 12 was missed, leading to the string "1113".

Constraints:

1 <= T <= 100
1 <= |S| <= 10⁴
The string S consists of digits 0 to 9
Numbers in the sequence have no more than six digits
Time Limit: 1 second

Note:

Ensure your solution correctly identifies the missing number or determines when to output -1.

Accepted Answer

The task is to find the missing number in a string of consecutive nonnegative integers.

Iterate through the string and check if each substring can form a valid number
If a substring forms a valid number, check if it is consecutive with the previous number
If a substring does not form a valid number or is not consecutive, it is the missing number
Handle edge cases such as multiple missing numbers or all numbers already present