【LeetCode】242. Valid Anagram（考察算法优化）

Question

Given two strings s and t, write a function to determine if t is an anagram of s.

For example,

s = “anagram”, t = “nagaram”, return true.

s = “rat”, t = “car”, return false.

Note:

You may assume the string contains only lowercase alphabets.

My code

bool isAnagram(string s, string t) {
sort(s.begin(), s.end());
sort(t.begin(), t.end());
return s==t;
}

However, my solution costs O(n logn).

O(n) solution:

class Solution {
public:
bool isAnagram(string s, string t) {
if(s.size() != t.size())    return false;

vector<int> vec(26, 0);

for(auto n : s)
++vec[n - 'a'];
for(auto n : t)
--vec[n - 'a'];

for(auto n : vec)
if(n != 0)  return false;

return true;
}
};