[LeetCode] Isomorphic Strings

Fri, 14 Jul 2017 03:38:23 +0000

This problem can be solved by using a hash map to store the mapping between the two strings. I initially thought it only contained lowercase letters, but it actually includes all ASCII characters. I started with one hash map, but since the mapping needs to be one-to-one, I ended up using two.

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class Solution {
public:
 bool isIsomorphic(string s, string t) {
 if (s.length() != t.length()) return false;
 char hash_s[256];
 char hash_t[256];
 memset(hash_s, NULL, 256);
 memset(hash_t, NULL, 256);
 for (int i = 0; i < s.length(); i++) {
 if (NULL == hash_s[s[i]] && NULL == hash_t[t[i]]) {
 hash_s[s[i]] = t[i];
 hash_t[t[i]] = s[i];
 }
 else {
 if (hash_s[s[i]] != t[i] || hash_t[t[i]] != s[i]) return false;
 }
 }
 return true;
 }
};

[LeetCode] Combine Two Tables

Fri, 14 Jul 2017 03:31:53 +0000

This problem is simply a table join query. However, I initially thought JOIN was the same as LEFT JOIN, and used WHERE instead of ON, which resulted in an inner join. I got it wrong several times.

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select p.FirstName, p.LastName, a.City, a.State
from Person as p
left join Address as a
on p.PersonId = a.PersonId

Programming Challenges on Coinidea's Blog

[LeetCode] Isomorphic Strings

[LeetCode] Combine Two Tables