3884.py

"""3884. First Matching Character From Both Ends
You are given a string s of length n consisting of lowercase English letters.
Return the smallest index i such that s[i] == s[n - i - 1].
If no such index exists, return -1.

 
Example 1:
Input: s = "abcacbd"
Output: 1
Explanation:
At index i = 1, s[1] and s[5] are both 'b'.
No smaller index satisfies the condition, so the answer is 1.

Example 2:
Input: s = "abc"
Output: 1
Explanation:
​​​​​​​At index i = 1, the two compared positions coincide, so both characters are 'b'.
No smaller index satisfies the condition, so the answer is 1.

Example 3:
Input: s = "abcdab"
Output: -1
Explanation:
​​​​​​​For every index i, the characters at positions i and n - i - 1 are different.
Therefore, no valid index exists, so the answer is -1."""






class Solution:
    def firstMatchingIndex(self, s: str) -> int:
        n = len(s)
        for i in range(n):
            if s[i] == s[n - i - 1]:
                return i
        return -1

# Test cases
if __name__ == "__main__":
    sol = Solution()
    
    test_cases = [
        "abcacbd",
        "abc",
        "abcdab"
    ]
    
    for s in test_cases:
        print(f"{s} => {sol.firstMatchingIndex(s)}")