P1082 同余方程（扩欧模板）

Posted 2022-06-10 war1111

https://www.luogu.org/problem/P1082

#include <iostream>
#include <cstdio>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstring>
#define inf 2147483647
#define N 1000010
#define p(a) putchar(a)
#define For(i,a,b) for(int i=a;i<=b;++i)

using namespace std;
int a,b,x,y;
void in(int &x)
    int y=1;char c=getchar();x=0;
    while(c<‘0‘||c>‘9‘)if(c==‘-‘)y=-1;c=getchar();
    while(c<=‘9‘&&c>=‘0‘) x=(x<<1)+(x<<3)+c-‘0‘;c=getchar();
    x*=y;

void o(int x)
    if(x<0)p(‘-‘);x=-x;
    if(x>9)o(x/10);
    p(x%10+‘0‘);


void exgcd(int a,int b,int &x,int &y)
    if(!b)
        x=1;
        y=0;
        return;
    
    exgcd(b,a%b,x,y);
    int t=x;
    x=y;
    y=t-(a/b)*y;


int main()
    in(a);in(b);
    exgcd(a,b,x,y);
    o((x%b+b)%b);
    return 0;