编译错误C ++

Question

dont know why i am gettion compilation error

prog.cpp: In function 'long long int modInverse(long long int, long long int)':
prog.cpp:46: error: 'extendedEuclid' was not declared in this scope

#include<stdio.h>
#include<utility>
#include<algorithm>
using namespace std;
#define MOD 1000000007
#define LL long long
LL factorial[2000005];
LL pow(LL a, LL b, LL mod) {
    LL x = 1, y = a;
    while(b > 0) {
        if(b%2 == 1) {
            x=(x*y);
            if(x>mod) x%=mod;
        }
        y = (y*y);
        if(y>mod) y%=mod;
            b /= 2;
    }
    return x;
}


LL modInverse(LL a, LL m) {
    return (extendedEuclid(a,m).second.first + m) % m;
}



pair<LL, pair<LL, LL> > extendedEuclid(LL a, LL b) {
    if(a == 0) return make_pair(b, make_pair(0, 1));
    pair<LL, pair<LL, LL> > p;
    p = extendedEuclid(b % a, a);
    return make_pair(p.first, make_pair(p.second.second - p.second.first*(b/a), p.second.first));
}


int main()
{

int t,a,b,n,i;
factorial[1]=1;
for (i=2;i<=2000001;i++)
    factorial[i]=(factorial[i-1]*i)%(MOD-1);
scanf("%d",&t);
while(t--)
{
    scanf("%d%d%d",&a,&b,&n);
    LL nCr=((factorial[2*n]%(MOD-1))*(modInverse(factorial[n],(MOD-1))))%(MOD-1);
    nCr=((nCr%(MOD-1))*(modInverse(factorial[n],(MOD-1))))%(MOD-1);
    LL nCr_pow_c=pow(nCr,b,MOD-1);
    LL a_pow_nCr_pow_c=pow(a,nCr_pow_c,MOD);
    printf("%lld\n",a_pow_nCr_pow_c);
}
return 0;
 }

Answer 1

Maybe because extendedEuclid isn't defined yet ?

You have to add its prototype before calling it.

Add pair<LL, pair<LL, LL> > extendedEuclid(LL a, LL b); on the top of your file and it'll work ;)

Answer 2

Put function declaration :- pair<LL, pair<LL, LL> > extendedEuclid(LL , LL );

before

LL modInverse(LL a, LL m) {
return (extendedEuclid(a,m).second.first + m) % m;
} 

Answer 3

You are trying to use extendedEuclid before it first appears. To fix it, you can move the modInverse function after the pair<LL, pair<LL, LL> > extendedEuclid(LL a, LL b) one. Alternatively, just add the declaration pair<LL, pair<LL, LL> > extendedEuclid(LL a, LL b); among your declarations early in the file.

Also, I would recommend you follow a good C++ tutorial or book of some kind, including coding style. Your code suggests that you've acquired a number of bad habits that may come from disorganized learning.