791. Custom Sort String**
https://leetcode.com/problems/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:
-
Shas length at most26, and no character is repeated inS. -
Thas length at most200. -
SandTconsist of lowercase letters only.
C++ 实现 1
使用哈希表, 统计 T 中每个字符的个数, 然后依次判断 S 中的每个字符是否出现在 T 中.
class Solution {
public:
string customSortString(string S, string T) {
unordered_map<char, int> record;
for (auto &c : T) record[c] ++;
string res;
for (auto &c : S) {
if (record.count(c)) {
res += string(record[c], c);
record.erase(c);
}
}
for (auto &p : record) res += string(p.second, p.first);
return res;
}
};