TLE in Foe Pairs (Educational Codeforces Round 10) - optimization

Question

On implementing O(N+M) complexity code for Foe Pairs problem
http://codeforces.com/contest/652/problem/C, I am getting TLE in Test Case 12.
Constraint : (1 ≤ N, M ≤ 3·105)
I am not getting, why for this constraint O(N+M) is getting TLE.
Here, is the code
#include<iostream>
#include<vector>
using namespace std;
int main()
{
int n,m;
cin>>n>>m;
std::vector<int> v(n+1);
for (int i = 0; i < n; ++i)
{
int x;
cin>>x;
v[x] = i;
}
std::vector<int> dp(n,0);
for (int i = 0; i < m; ++i)
{
int a,b;
cin>>a>>b;
if(v[a]>v[b])
swap(a,b);
dp[v[b]] = max(dp[v[b]], v[a]+1);
}
for (int i = 1; i < n; ++i)
{
dp[i] = max(dp[i], dp[i-1]);
}
long long s = 0;
for (int i = 0; i < n; ++i)
{
s+=(i+1-dp[i]);
}
cout<<s;
}
Is there anything, I am missing?

Answer 1

I changed all cin to scanf, it passed all test cases : http://codeforces.com/contest/652/submission/17014495
#include<cstdio>
#include<iostream>
#include<vector>
using namespace std;
int main()
{
int n,m;
scanf("%d%d", &n, &m);
//cin>>n>>m;
std::vector<int> v(n+1);
for (int i = 0; i < n; ++i)
{
int x;
//cin>>x;
scanf("%d", &x);
v[x] = i;
}
std::vector<int> dp(n,0);
for (int i = 0; i < m; ++i)
{
int a,b;
//cin>>a>>b;
scanf("%d%d", &a, &b);
if(v[a]>v[b])
swap(a,b);
dp[v[b]] = max(dp[v[b]], v[a]+1);
}
for (int i = 1; i < n; ++i)
{
dp[i] = max(dp[i], dp[i-1]);
}
long long s = 0;
for (int i = 0; i < n; ++i)
{
s+=(i+1-dp[i]);
}
cout<<s;
return 0;
}
You should always try to use scanf when the amount of input is large as it is faster.
You can read more about scanf being faster here : Using scanf() in C++ programs is faster than using cin?