Cin vs scanf in cpp (more faster)

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i stuck at a problem SPOJ.com - Problem OLOLO[^]

I am taking XOR of all the value finally all values that are coming two times will be canceled and remaining value will be ans

1) I used

cin>>temp

with

std::ios::sync_with_stdio(false);

in while loop getting "WA" (I used above line Using scanf() in C++ programs is faster than using cin? - Stack Overflow[^] )
And time complexity was tight

2)only used cin>>temp got TLE

3)used only

scanf("%d",&temp)

accepted

What I have tried:

C++

#include<bits/stdc++.h>
using namespace std;
int main(){
    long long int t;
    cin>>t;
    std::ios::sync_with_stdio(false);
    long long int ans=0;
    while(t--){
        long long int temp;
        cin>>temp;
        ans=ans^temp;

    }
    cout<<ans;
}

can someone explain why my answer not get accepted in first case according to post I did the same

Posted 12-Jan-19 12:27pm

kavinderrana121

Updated 14-Jan-19 9:24am

KarstenK

v3

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Richard MacCutchan 14-Jan-19 6:45am

You need to ask the people at SPOJ.com.

2 solutions

Solution 1

one of the reason could be a negative input which will cause while loop endlessly.

Posted 13-Jan-19 23:13pm

Manish K. Agarwal

Comments

Patrice T 14-Jan-19 15:03pm

Since it is a contest, I think the input is the same in both cases.

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Patrice T · Accepted Answer · 2019-01-14T09:24:00

Quote:
Cin vs scanf in cpp (more faster)

Answer to this question depends on implantation details of site compiler which we don't have. Simply, it is common to see c++ code slower than c.

If you want your code faster, you need to understand how time is spent. Your code spend a lot of time converting a string of chars input to integer. When you know how time is spend, the next question is 'is there another path?'.
Do you really need that conversion ?
In fact, no.
Think how to handle input if it was names. In C/C++, a char is a 8 bits integer, so
'A'^'B'^'A' is allowed and works the same as with an integer.
I let you handle details as an exercise.