Luo Gu P1082 congruence equation (exgcd)

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Problem-solving ideas:

Because the derivation process is too complicated, too lazy to write, so the solution to a problem Portal

AC Code:

 1 #include<iostream>
 2 #include<cstdio>
 3 
 4 using namespace std;
 5 
 6 long long a,b,x,y;
 7 
 8 void exgcd(long long p,long long o) {
 9     if(o == 0) {
10         x = 1;
11         y = 0;
12         return ;
13     }
14     exgcd(o,p % o);
15     long long tx = x;
16     x = y;
17     y = tx - p / o * y; 
18 }
19 
20 int main() {
21     cin >> a >> b;
22     exgcd(a,b);
23     x = (x % b + b) % b;
24     printf("%lld",x);
25     return 0;
26 }