First Unique Character in a String

Description

Given a string, find the first non-repeating character in it and return its index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.
s = "loveleetcode"
return 2.

 

Note: You may assume the string contains only lowercase English letters.

Solution(javascript)

/**
 * @param {string} s
 * @return {number}
 */
var firstUniqChar = function(s) {
    const map = {}
    for(let c of s) {
        map[c] = (map[c] || 0) + 1
    }
    for(let i = 0; i < s.length; i++) {
        const c = s[i]
        if(map[c] === 1) {
            return i
        }
    }
    return -1
};