LeetCode 383. 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

好多天没写代码了，这样不行啊。。。
简单题，用哈希可以解决，O(n);
bool canConstruct(char* ransomNote, char* magazine) {
int m[26] = {0};
int r[26] = {0};
int i;
for(i = 0; magazine[i] != '\0'; i ++){
m[magazine[i] - 'a'] ++;
}
for(i = 0; ransomNote[i] != '\0'; i ++){
r[ransomNote[i] - 'a'] ++;
}
for(i = 0; i < 26;){
if(r[i]){
if(m[i]){
m[i] --;
r[i] --;
}else
return false;
}
if(!r[i]) i ++;
}
return true;
}