136. Single Number

느낌이 다른 풀이 3가지

const singleNumber = function(nums) {
    const obj = {}
    for (let num of nums) {
        obj[num] ? obj[num]++ : obj[num] = 1 

    }
    for (const [k, v] of Object.entries(obj)) {
        if (v == 1) {
           return k
        }
    }

};

function singleNumber(nums) {
  const map = {};
  for (let n of nums) {
    if (map[n] == null) map[n] = 0;
    map[n]++;
  }

  for (let n in map) {
    if (map[n] === 1) return Number(n);
  }
}

const singleNumber = function(nums) {
    let hash = {}
    for(let val of nums){
        hash[val]?delete hash[val]:hash[val]=1;
    }
    return Object.keys(hash)[0]
};