[校内赛3-1][题解]folder

题目其实非常裸……

就是让你求ax≡c(mod b)中x的最小正整数解

裴蜀定理判断是否有解（即信息真假）

然后exgcd解方程

输出有坑不过我相信你们没有人会踩因为我已经提示了

std：

#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<ctime>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<bitset>
#include<set>
#include<map>
#define LL long long
#define rg register
#define us unsigned
#define eps 1e-6
#define INF 0x3f3f3f3f
#define ls k<<1
#define rs k<<1|1
#define tmid ((tr[k].l+tr[k].r)>>1)
#define nmid ((l+r)>>1)
#define Thispoint tr[k].l==tr[k].r
#define pushup tr[k].wei=tr[ls].wei+tr[rs].wei
using namespace std;
inline void Read(LL &x){
    LL f=1;
    char c=getchar();
    x=0;
    while(c<'0'||c>'9'){
        if(c=='-')f=-1;
        c=getchar();
    }
    while(c>='0'&&c<='9'){
        x=(x<<3)+(x<<1)+c-'0';
        c=getchar();
    }
    x*=f;
}

LL a,b,c,x,y;
LL Gcd(LL a,LL b){
    return b==0?a:Gcd(b,a%b);
}
void exgcd(LL a,LL b,LL &x,LL &y){
    if(b==0){
        x=1,y=1;
        return;
    }
    LL x_1,y_1;
    exgcd(b,a%b,x_1,y_1);
    x=y_1;
    y=x_1-(a/b)*y_1;
}
int main(){
    freopen("folder.in","r",stdin);
    freopen("folder.out","w",stdout);
    Read(a),Read(b),Read(c);
    LL g=Gcd(a,b);
    if(c%g!=0){//裴蜀定理判断 
        printf("N0
O
");
        return 0;
    }
    exgcd(a,b,x,y);
    LL s=b/Gcd(a,b);//此处取模可以参照之前的课件，这里不再赘述 
    printf("YE5
%lld
",((x*c/g)%s+s)%s);
    return 0;
}