383. Ransom Note【easy】

383. Ransom Note【easy】

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

解法一：

 class Solution {
 public:
     bool canConstruct(string ransomNote, string magazine) {
         map<char, int> m_rans;

         for (int i = ; i < ransomNote.length(); ++i) {
             ++m_rans[ransomNote[i]];
         }

         for (int i = ; i < magazine.length(); ++i) {
             if (m_rans.find(magazine[i]) != m_rans.end()) {
                 --m_rans[magazine[i]];
             }
         }

         for (map<char, int>::iterator it = m_rans.begin(); it != m_rans.end(); ++it) {
             if (it->second > ) {
                 return false;
             }
         }

         return true;
     }
 };

解法二：

 public class Solution {
     public boolean canConstruct(String ransomNote, String magazine) {
         int[] arr = new int[];
         for (int i = ; i < magazine.length(); i++) {
             arr[magazine.charAt(i) - 'a']++;
         }
         for (int i = ; i < ransomNote.length(); i++) {
             if(--arr[ransomNote.charAt(i)-'a'] < ) {
                 return false;
             }
         }
         return true;
     }
 }

参考@yidongwang 的代码。

解法三：

 class Solution {
 public:
     bool canConstruct(string ransomNote, string magazine) {
         unordered_map<char, int> map();
         for (int i = ; i < magazine.size(); ++i)
             ++map[magazine[i]];
         for (int j = ; j < ransomNote.size(); ++j)
             if (--map[ransomNote[j]] < )
                 return false;
         return true;
     }
 };

参考@haruhiku 的代码

解法四：

 class Solution {
 public:
     bool canConstruct(string ransomNote, string magazine) {
         vector<int> vec(, );
         for (int i = ; i < magazine.size(); ++i)
             ++vec[magazine[i] - 'a'];
         for (int j = ; j < ransomNote.size(); ++j)
             if (--vec[ransomNote[j] - 'a'] < )
                 return false;
         return true;
     }
 };

参考@haruhiku 的代码