实现代码如下:
void exEuclidean(int a,int b,int &s,int &t){
int r1 = a, r2 = b , s1 = 1, s2 = 0, t1 = 0, t2 = 1;//初始化
int q,r;
while(r2 > 0)
{
q = r1 / r2;
r = r1 - q * r2; //也就是r = r1%r2;
r1 = r2;
r2 = r;
s = s1 - q * s2;
s1 = s2;
s2 = s;
t = t1 - q * t2;
t1 = t2;
t2 = t;
}
//gcd(a,b) = r1;
s = s1;
t = t1;
}
int findReverse(int a,int n){ //找出a关于n的乘法逆
int s,t;
exEuclidean(n,a,s,t); //因为传引用,s和t得到解了
int a_ = (t >= 0) ? (t % n) : ((t-t*n)%n); //乘法逆就是t映射于n的值
return a_;
}
string encode(string text,int addKey,int mulKey){
string password = "";
for(int i = 0 ; i < text.size(); i++){
int code = text[i] - 'a';
password += (code * mulKey + addKey) % 26 + 'A';
}
return password;//得到密文
}
string decode(string password,int addKey,int mulKey)