Shortest Distance to a Character

From LeetCode

problem description / sulution

Solution in Python3

class Solution:
    def shortestToChar(self, S: str, C: str) -> List[int]:
        shortest_dist = []
        dist = float('inf')
        for c in S:
            if c == C:
                dist = 0
            else:
                dist += 1
            shortest_dist.append(dist)
        
        dist = float('inf')
        for c, i in enumerate(S[::-1]):
            if c == C:
                dist = 0
            else:
                dist += 1
            shortest_dist[l - i] = min(shortest_dist[i], dist)

        return shortest_dist    
            

I am lucky to get

Runtime: 48 ms, faster than 87.25% of Python3 online submissions for Shortest Distance to a Character.

Time Complexity

\(O(l)\), where \(l\) is the length of S.