题目：http://acm.timus.ru/problem.aspx?space=1&num=1132
很无奈的一个题，看解题报告没看懂怎么回事，问的队友，然后不知道他怎么找的那些资料，然后我就是直接看的链接，
http://en.wikipedia.org/wiki/Tonelli%E2%80%93Shanks_algorithm
再加上 n == 2时特判，然后就是 r == n - r 时，输出一个，然后就是按照那个算法步骤算了
View Code
1 typedef long long ll; 2 ll tmod; 3 ll mod(ll n,ll p) 4 { 5 ll temp = 1; 6 while(p > 0) 7 { 8 if(p & 1) temp = temp * n % tmod; 9 n = n * n % tmod; 10 p /= 2; 11 } 12 return temp; 13 } 14 ll pows(ll n) 15 { 16 ll i; 17 ll temp = 1; 18 for(i = 0; i < n; i++) 19 temp *= 2; 20 return temp; 21 } 22 23 int main() 24 { 25 int n,p,cs; 26 ll z,q,s,c; 27 ll r,t,m,b,i; 28 ll minx; 29 scanf("%d",&cs); 30 while(cs--) 31 { 32 scanf("%d%d",&n,&p); 33 if(p == 2) 34 { 35 if(n % p == 1)printf("1\n"); 36 else printf("No root\n"); 37 continue; 38 } 39 tmod = p; 40 if(mod(n,(p - 1) / 2) != 1) {printf("No root\n"); continue;} 41 q = p - 1; 42 s = 0; 43 while(q % 2 == 0) 44 { 45 q /= 2; 46 s ++; 47 } 48 if(s == 1) 49 { 50 r = mod(n,(p + 1) / 4); 51 } 52 else 53 { 54 while(1) 55 { 56 z = 1 + rand() % (p - 1); 57 if(mod(z,(p - 1) / 2) == (p - 1)) break; 58 } 59 c = mod(z,q); 60 r = mod(n,(1 + q) / 2); 61 t = mod(n,q); 62 m = s; 63 while(1) 64 { 65 if(t % p == 1) break; 66 for(i = 1; i < m; i++) 67 { 68 if(mod(t,pows(i)) == 1) break; 69 } 70 b = mod(c, pows(m - i - 1)); 71 r = r * b % p; 72 t = t * b * b % p; 73 c = b * b % p; 74 m = i; 75 } 76 } 77 r = (r % p + p) % p; 78 if(r == p - r)cout<<r<<endl; 79 else 80 { 81 minx = Min(r,p - r); 82 cout<<minx<<" "<<(p - minx)<<endl; 83 } 84 } 85 return 0; 86 }