Isomorphic Strings

2015.4.30 15:54

Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

For example,
Given "egg""add", return true.

Given "foo""bar", return false.

Given "paper""title", return true.

Note:
You may assume both s and t have the same length.

Solution:

Think about the string pair "abb" and "cdd". An isomorphic pair is like one-to-one mapping. So we use the basic priniciple: injective + surjective = bijective.

Check if the mapping from s to t is onto, and t to s as well. If both hold, they're isomorphic.

Accepted code:

 1 #include <cstring>
2 using namespace std;
3
4 class Solution {
5 public:
6     bool isIsomorphic(string s, string t) {
7         return check(s, t) && check(t, s);
8     }
9 private:
10     bool check(string s, string t) {
11         char a[256];
12
13         memset(a, 0, sizeof(a));
14         int i;
15         int n = s.length();
16
17         for (i = 0; i < n; ++i) {
18             if (a[s[i]] == 0) {
19                 a[s[i]] = t[i];
20             }
21             s[i] = a[s[i]];
22         }
23
24         return s == t;
25     }
26 };

posted on 2015-04-30 16:03  zhuli19901106  阅读(278)  评论(0编辑  收藏  举报