383. Ransom Note

原题网址：https://leetcode.com/problems/ransom-note/

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

方法：直方图频率统计。

public class Solution {
private int[] frequency(String s) {
int[] f = new int[26];
char[] sa = s.toCharArray();
for(char c : sa) {
f[c - 'a'] ++;
}
return f;
}
public boolean canConstruct(String ransomNote, String magazine) {
int[] fr = frequency(ransomNote);
int[] fm = frequency(magazine);
for(int i = 0; i < fr.length; i++) {
if (fr[i] > fm[i]) {
return false;
}
}
return true;
}
}