[LeetCode]Isomorphic Strings

题目描述:(链接)

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.

解题思路：

用哈希表来存储字符出现的位置，然后比较同型字符出现的位置，如果不等返回false。

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        int len = s.size();
        
        unordered_map<int, int> cache1;
        unordered_map<int, int> cache2;
        for (int i = 0; i < len; ++i) {
            auto c1 = cache1.find(s[i]);
            auto c2 = cache2.find(t[i]);
            
            if (c1 == cache1.end() && c2 == cache2.end()) {
                cache1[s[i]] = i;
                cache2[t[i]] = i;
            } else if ((c1 == cache1.end() && c2 != cache2.end()) || 
                      (c1 != cache1.end() && c2 == cache2.end()) || 
                      (c1->second != c2->second)) {
                return false;
            }
        }
        
        return true;
    }
};