136. Single Number leetcode

singleNumber.ts

function singleNumber(nums: number[]) {

     let set= new Set<number>();
        for(let i of nums){
            if(set.has(i)){
                set.delete(i);
            }else{
                set.add(i);
            }
        }
        for(let i of set){
            return i;
        }
        return -1;
    }