[LeetCode] 821. Shortest Distance to a Character_Easy tag: BFS

Given a string S and a character C, return an array of integers representing the shortest distance from the character C in the string.

Example 1:

Input: S = "loveleetcode", C = 'e'
Output: [3, 2, 1, 0, 1, 0, 0, 1, 2, 2, 1, 0]

 

Note:

1. S string length is in [1, 10000].
2. C is a single character, and guaranteed to be in string S.
3. All letters in S and C are lowercase.

思路为BFS, 类似于[LeetCode] 286. Walls and Gates_Medium tag: BFS.

Code

class Solution(object):
    def shortestToChar(self, S, C):
        """
        :type S: str
        :type C: str
        :rtype: List[int]
        """
        queue, visited, ans, l = collections.deque(), set(), [0]*len(S), len(S)
        for index, ch in enumerate(S):
            if ch == C:
                queue.append((index,0))
                visited.add(index)
        while queue:
            node, dis = queue.popleft()
            for d in [-1,1]:
                n_index = node + d
                if 0 <= n_index < l and n_index not in visited:
                    ans[n_index] = dis + 1
                    visited.add(n_index)
                    queue.append((n_index, dis + 1))
        return ans