Question

Suppose I have a std::vector A. This vector has only values in the range of 0 to A.size(), inclusive. For example, if there are 5 values in A, then the only values it can have are {0, 1, 2, 3, 4, 5}, although not necessarily in that order. Duplicate values might be present too.

Obviously, at least one value is missing. Using O(n) time and O(n) space, where n is A.size(), determine which value(s) are missing from the vector.

Answer 1

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#include <bits/stdc++.h>
using namespace std;

int main() {
vector<int> v{1,5,3,4,0};
int sum=0;
for(auto it :v )
sum+=it;
int n = v.size();
n= (n*(n+1))/2;
cout<<n-sum;
   return 0;
}