[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

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方法一：暴力法
bool canConstruct(string ransomNote, string magazine)
{ int lenR=ransomNote.length();
int lenM=magazine.length();
int flag=0;
if(lenR>lenM)
return false;
int *vis=new int [lenM];
memset(vis,1,lenM*sizeof(int));
for(int i=0;i<lenR;i++)
{
flag=0;
for(int j=0;j<lenM;j++)
{
if(ransomNote[i]==magazine[j]&&vis[j])
{
vis[j]=0;
flag=1;
break;
}
}
if(flag!=1)
return false;
}
return true;
}方法二：

bool canConstruct(string ransomNote, string magazine)
{
int a[26]={0};
int lenR=ransomNote.length();
int lenM=magazine.length();
for(int i=0;i<lenM;i++)
{
a[magazine[i]-'a']++;
}
for(int j=0;j<lenR;j++)
{
if(a[ransomNote[j]-'a']>0)
{
a[ransomNote[j]-'a']--;
}
else
return false;
}
return true;
}