Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1.
Examples:
s = "leetcode"
return 0.
s = "loveleetcode",
return 2.
Note: You may assume the string contain only lowercase letters.
Solution:
class Solution {
public int firstUniqChar(String s) {
Map<Character, Integer> freq = new HashMap<>();
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
freq.put(c, freq.getOrDefault(c, 0) + 1);
}
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (freq.get(c) == 1) {
return i;
}
}
return -1;
}
}