leetcode-Missing Number

Difficulty: Medium

Given an array containing n distinct numbers taken from0, 1, 2, ..., n, find the one that is missing from the array.

For example,
Given nums = [0, 1, 3] return 2.

Note:
Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?

class Solution {public:    int missingNumber(vector<int>& nums) {        if(nums.empty())            return -1;        int size=nums.size()/32+1;                int bitmap[size];        fill(bitmap,bitmap+size,0);        int maxNum=nums[0];        for(auto &e:nums){            bitmap[e/32]|=(1<<(e%32));            maxNum=max(e,maxNum);        }                for(int i=0;i<maxNum;++i){            if(bitmap[i/32]&(1<<(i%32)))                continue;            else                            return i;        }        return maxNum+1;            }};