版权声明:转载请说明出处:https://blog.csdn.net/hanyanwei123 https://blog.csdn.net/hanyanwei123/article/details/81635741
The modular modular multiplicative inverse of an integer a modulo m is an integer x such that a-1≡x (mod m)
. This is equivalent to ax≡1 (mod m)
.
Input
There are multiple test cases. The first line of input is an integer T ≈ 2000 indicating the number of test cases.
Each test case contains two integers 0 < a ≤ 1000 and 0 < m ≤ 1000.
Output
For each test case, output the smallest positive x. If such x doesn’t exist, output “Not Exist”.
Sample Input
3 3 11 4 12 5 13
Sample Output
4 Not Exist 8
References
#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<string>
#include<math.h>
#include<string.h>
using namespace std;
int T;
int a,m;
int exgcd(int A,int B,int &x,int &y){
if(B==0){
x=1;
y=0;
return A;
}
int d=exgcd(B,A%B,x,y);
int temp=x;
x=y;
y=temp-A/B*y;
return d;
}
int main()
{
scanf("%d",&T);
while(T--){
scanf("%d %d",&a,&m);
int x,y;
int gcd =exgcd(a,m,x,y);
if(gcd==1){//互质才有解
x%=m;
if(x<=0)x+m;
printf("%d\n",x);
}
else {
printf("Not Exist\n");
}
}
return 0;
}