821. Shortest Distance to a Character

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821. Shortest Distance to a Character

题目描述

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:

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

题目大意

给定字符串 S 和字符 C ，求 S 中每个字符距离 C 字符最小距离。

解题思路

正向反向遍历，求最小。

代码

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class Solution {
    func shortestToChar(_ S: String, _ C: Character) -> [Int] {
        var ans = Array(repeating: S.count, count: S.count)
        var last = -(ans.count * 2 + 1)
        for (i, char) in S.enumerated() {
            if char == C { last = i }
            ans[i] = min(i - last, ans[i])
        }
        last = ans.count * 2 + 1
        for (i, char) in S.enumerated().reversed() {
            if char == C { last = i }
            ans[i] = min(last - i, ans[i])
        }
        return ans
    }
}
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