268. Missing Number

Given an array containing n distinct numbers taken from

0, 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?

Credits:

Special thanks to
@jianchao.li.fighter for adding this problem and creating all test cases.

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class Solution {
public:
int missingNumber(vector<int>& nums) {
double sum=(nums.size())*(nums.size()+1)/2;
for(int i=0;i<nums.size();++i)
{
sum-=nums[i];
}
return sum;
}
};