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First Unique Character in a String

Problem Statement​

Given an unsorted integer array nums, return the smallest missing positive integer.

You must implement an algorithm that runs in O(n) time and uses constant extra space.

Leetcode link

Example 1:​

Input: s = "leetcode"
Output: 0

Example 2:​

Input: s = "loveleetcode"
Output: 2

Example 3:​

Input: s = "aabb"
Output: -1

Constraints:​

  • 1 <= s.length <= 105
  • s consists of only lowercase English letters.

Code​

Python Code

class Solution(object):
    def firstUniqChar(self, s):
        """
        :type s: str
        :rtype: int
        """
        d = dict()

        for i in range(len(s)):
            if d.setdefault(s[i],[]) or True:
                d[s[i]].append(i)

        for i in range(len(s)):
            if len(d[s[i]]) == 1:
                return(i)

        return(-1)