[Leetcode] Ransom Note

A very typical application of hash maps. Since I am now learning Java, I code in Java. The following code uses ToCharArray () and Getordefault (), which is learnt from this post.

 Public classSolution { Public Booleancanconstruct (String ransomnote, String magazine) {HashMap<character, integer> map =NewHashmap<>();  for(Character K:magazine.tochararray ()) {intv = map.getordefault (k, 0) + 1;        Map.put (k, v); }         for(Character K:ransomnote.tochararray ()) {intv = map.getordefault (k, 0)-1; if(v < 0)return false;        Map.put (k, v); }        return true; }}

This code takes is about 60ms.

In fact, arrays can is used to replace hash maps since the test cases of this problem only contan the Chinese letters. A array-version solution can be found here and is rewritten below.

 Public classSolution { Public Booleancanconstruct (String ransomnote, String magazine) {int[] Map =New int[26];  for(CharK:magazine.tochararray ()) Map[k-' A ']++;  for(CharK:ransomnote.tochararray ()) {            intv =--map[k-' a ']; if(v < 0)return false; }        return true; }}

This version was much faster, about 13MS.

[Leetcode] Ransom Note