Efficient Solution Using String Manipulation C++
Intuitionwe can treat each number as a string, so its digits become accessible as characters. These characters can then be converted back to integers and added
# Intuition
we can treat each number as a string, so its digits become accessible as characters. These characters can then be converted back to integers and added to the result vector.

# Approach
1. Iterate Over Each Number: For every number in nums, convert it to a string using ```to_string()```.

    Example: ```123 -> "123"```.
2. Extract Each Digit: Loop through each character of the string representation. Each character corresponds to a single digit of the number.

    Example: ```"123" -> '1', '2', '3'```.
3. Convert Characters to Integers: Subtract '0' from each character to get its integer equivalent.

    Example: ```'1' - '0' -> 1```.
4. Append to Result: Push each digit into the result vector.

5. Return the Result: After processing all numbers in ```nums```, return the ```result``` vector.

# Complexity
- Time complexity:
$$O(n*k)$$

- Space complexity:
$$O(n*k)$$

# Code
```cpp []
class Solution {
public:
    vector<int> separateDigits(vector<int>& nums) {
      vector<int> result;
      for(auto &num : nums)
        for(auto &s : to_string(num))
          result.push_back(s - '0');
      return result;
    }
};
```
['C++']