First Non-Repeating Character Index

Medium

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Example 1:

Input: s = "leetcode"
Output: 0

Explanation: 'l' is the first character that appears only once, and its index is 0.

Example 2:

Input: s = "loveleetcode"
Output: 2

Explanation: 'l' appears twice, 'o' appears twice. 'v' is the first character that appears only once, and its index is 2.

Example 3:

Input: s = "aabb"
Output: -1

Explanation: All characters appear multiple times.

Example 1

Input

[
  "leetcode"
]

Output

Explanation. The character 'l' appears only once at index 0. 'e' appears multiple times.

Example 2

Input

[
  "loveleetcode"
]

Output

Explanation. The characters 'l' and 'o' repeat. The character 'v' appears only once at index 2.

Example 3

Input

[
  "aabb"
]

Output

-1

Explanation. All characters ('a' and 'b') repeat, so there is no non-repeating character.

Example 4

Input

[
  "abcabcde"
]

Output

Explanation. Characters 'a', 'b', 'c' all repeat. The character 'd' appears only once at index 6.

Example 5

Input

[
  "z"
]

Output

Explanation. The character 'z' appears only once at index 0.

Example 6

Input

[
  ""
]

Output

-1

Explanation. An empty string contains no characters, thus no non-repeating character.

Follow-up: Can you solve this problem using only one pass through the string?

Constraints:

The string `s` will consist only of lowercase English letters. The length of `s` will be between `0` and `10^5`.

Views: 10

First Non-Repeating Character Index

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Example 2:

Example 3:

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First Non-Repeating Character Index

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