### Letscode_sundar's blog

By Letscode_sundar, history, 17 months ago,

I was doing this problem and i noticed a strange thing.

In order to calculate sum of the vector elements , I used the accumulate function available in STL

typedef long long ll;
#define int ll
//the sum variable and elements in vector becomes long long type
int sum=0;
sum=accumulate(v.begin(),v.end(),0);


127183042

This basically gives the wrong answer .

But

#define int ll
int sum=0;
sum=accumulate(v.begin(),v.end(),sum);
or
sum=accumulate(v.begin(),v.end(),0LL);



127184828

gets accepted.

#### Why is this happening ?

All these days, I thought it is just an initial value that we give to the accumulate function (the last argument), but it is not just an initial value and plays a big role in the outcome of the sum.

I am telling it isn't just a value because

ll sum=10;
sum+=20;


Now it wouldn't matter if 20 is given in LL or not , but here 0 gives WA but 0LL is accepted.

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