Check whether given string can be generated after concatenating given strings

Given three strings str, A and B. The task is to check whether str = A + B or str = B + A where + denotes concatenation. 
Examples: 
 

Input: str = "GeeksforGeeks", A = "Geeksfo", B = "rGeeks" 
Output: Yes 
str = A + B = "Geeksfo" + "rGeeks" = "GeeksforGeeks"
Input: str = "Delhicapitals", B = "Delmi", C = "capitals" 
Output: No 
 

Approach: 
 

1. If len(str) != len(A) + len(B) then it is not possible to generate str by concatenating a + b or b + a.
2. Else check whether str starts with a and ends with b or it starts with b and ends with a. Print Yes if any of these is true else print No

Below is the implementation of the above approach:
 

Yes

Time Complexity: O(max(a,b,c)), as we are using a loop to traverse a, b, and c times. Where a, b, and c are the length of the strings.

Auxiliary Space: O(1), as we are not using any extra space.