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missing number.cpp
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missing number.cpp
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/*
hare krishna hare krishna krishna krishna hare hare
hare rama hare rama rama rama hare hare
#6
*/
//find missing number in array
#include<bits/stdc++.h>
#define ll long long int
#define ull long long
#define pb push_back
#define mp make_pair
#define mod 1000000007
#define forp(i,n) for(int i=0;i<n;i++)
#define forn(i,n) for(int i=n-1;i>=0;i--)
#define fast ios_base::sync_with_stdio(false);
using namespace std;
void solve1(int arr[],int n)
{
int t= (n+1)*(n+2)/2,s=0;
forp(i,n)
s+=arr[i];
cout<<t-s<<endl;
}
void solve2(int arr[],int n) //for big number
{
int s=1;
for(int i=2;i<=n+1;i++)
{
s=s-arr[i-2]+i;
}
cout<<s<<endl;
}
void solve3(int arr[],int n) //using xor
{
int a=arr[0];
int b=1;
for(int i=1;i<n;i++)
a=a^arr[i];
for(int i=2;i<=n+1;i++)
b=b^i;
cout<<(a^b);
}
int main()
{
fast
int arr[]={1,4,6,3,7,2};
int n=sizeof(arr)/sizeof(arr[0]);
solve1(arr,n);
solve2(arr,n);
solve3(arr,n);
return 0;
}