Shortest Distance to a Character

Shortest Distance to a Character.py

class Solution:
    def shortestToChar(self, S, C):
        """
        :type S: str
        :type C: str
        :rtype: List[int]
        """
        n = len(S)
        
        result = [n for i in range (n)]
        
        left, right = -n , 2*n
        
        for  i in range(n):
            j = n -1 - i
            if S[i] == C:
                left = i
            if S[j] == C:
                right = j
            
            result[i] = min(result[i], dist(i, left))
            result[j] = min(result[j], dist(j, right))
            
        return result
            
        
def   dist(a,b):
        if a -b >0 :
            return a-b 
        else:
            return b -a