791 Custom Sort String

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791. Custom Sort String

题目描述

S and T are strings composed of lowercase letters. In S, no letter occurs more than once.

S was sorted in some custom order previously. We want to permute the characters of T so that they match the order that S was sorted. More specifically, if x occurs before y in S, then x should occur before y in the returned string.

Return any permutation of T (as a string) that satisfies this property.

Example :
Input:
S = “cba”
T = “abcd”
Output: “cbad”
Explanation:
“a”, “b”, “c” appear in S, so the order of “a”, “b”, “c” should be “c”, “b”, and “a”.
Since “d” does not appear in S, it can be at any position in T. “dcba”, “cdba”, “cbda” are also valid outputs.

Note:

S has length at most 26, and no character is repeated in S.
T has length at most 200.
S and T consist of lowercase letters only.

题目大意

根据 S 给定的字母顺序，对 T 进行排序，S 中不存在的字母按照原有顺序排列在尾部。

解题思路

选择排序思路。

代码

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class Solution {
    func customSortString(_ S: String, _ T: String) -> String {
        var sArr = Array(S)
        var tArr = Array(T)
        var index = 0
        for i in 0..<sArr.count {
            for j in index..<tArr.count {
                if tArr[j] == sArr[i] {
                    tArr[j] = tArr[index]
                    tArr[index] = sArr[i]
                    index += 1
                }
            }
        }
        return String(tArr)
    }
}
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