387. First Unique Character in a String
1. Description
Given a string, find the first non-repeating character in it and return its index. If it doesn’t exist, return -1.
2. Example
Example 1:
s = “leetcode”
return 0.
s = “loveleetcode”
return 2.
3. Note
- You may assume the string contains only lowercase English letters.
4. Solutions
My Accepted Solution
n = i_str.size()
Time complexity: O(n)
Space complexity: O(n)
class Solution
{
public:
// int firstUniqChar(string s)
int firstUniqChar(string &i_str)
{
vector<int> letterTimes(26);
for(int i = 0; i < i_str.size(); i++)
letterTimes[i_str[i] - 'a']++;
for(int i = 0; i < i_str.size(); i++)
{
if(letterTimes[i_str[i] - 'a'] == 1)
return i;
}
return -1;
}
};