383. Ransom Note - jiejackyzhang/leetcode-note GitHub Wiki
Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false.
Each letter in the magazine string can only be used once in your ransom note.
Note:
You may assume that both strings contain only lowercase letters.
canConstruct("a", "b") -> false
canConstruct("aa", "ab") -> false
canConstruct("aa", "aab") -> true
String类题目。
可采用hash map。当然，如果只有小写英文字母，也可以采用固定长度为26的数组来保存数据。
public class Solution {
public boolean canConstruct(String ransomNote, String magazine) {
Map<Character, Integer> map = new HashMap<Character, Integer>();
for(int i = 0; i < magazine.length(); i++) {
char c = magazine.charAt(i);
map.put(c, map.containsKey(c) ? map.get(c)+1 : 1);
}
for(int i = 0; i < ransomNote.length(); i++) {
char c = ransomNote.charAt(i);
if(!map.containsKey(c)) return false;
int count = map.get(c);
if(count == 0) return false;
map.put(c, count-1);
}
return true;
}
}