面试题50 第一个只出现一次的字符

示例

js

s = "abaccdeff"
返回 "b"

s = "" 
返回 " "

JS

js

/**
 * @param {string} s
 * @return {character}
 */
var firstUniqChar = function (s) {
    let map = {}
    for (c of s) {
        if (map[c]) {
            map[c]++;
        } else {
            map[c] = 1
        }
    }
    for (c of s) {
        if (map[c] === 1) {
            return c
        }
    }
    return ' '
};