题目链接：
https://codeforces.com/contest/707/problem/C
题目：
题意：
告诉你直角三角形的一条边，要你输出另外两条边。
思路：
我们容易发现除2外的所有素数x作为直角边，那么另外两条边的长度一定为(x * x - 1)/2和(x * x + 1)/2，因此对于每个数我们只需要找到n的最小素因子（除2外）即可，需要额外处理一下2的幂次。
代码实现如下：
1 #include <set> 2 #include <map> 3 #include <deque> 4 #include <queue> 5 #include <stack> 6 #include <cmath> 7 #include <ctime> 8 #include <bitset> 9 #include <cstdio> 10 #include <string> 11 #include <vector> 12 #include <cstdlib> 13 #include <cstring> 14 #include <iostream> 15 #include <algorithm> 16 using namespace std; 17 18 typedef long long LL; 19 typedef pair<LL, LL> pLL; 20 typedef pair<LL, int> pLi; 21 typedef pair<int, LL> pil;; 22 typedef pair<int, int> pii; 23 typedef unsigned long long uLL; 24 25 #define lson rt<<1 26 #define rson rt<<1|1 27 #define lowbit(x) x&(-x) 28 #define name2str(name) (#name) 29 #define bug printf("*********\n") 30 #define debug(x) cout<<#x"=["<<x<<"]" <<endl 31 #define FIN freopen("D://code//in.txt","r",stdin) 32 #define IO ios::sync_with_stdio(false),cin.tie(0) 33 34 const double eps = 1e-8; 35 const int mod = 1000000007; 36 const int maxn = 2e5 + 7; 37 const double pi = acos(-1); 38 const int inf = 0x3f3f3f3f; 39 const LL INF = 0x3f3f3f3f3f3f3f3fLL; 40 41 LL t; 42 43 int main(){ 44 scanf("%lld", &t); 45 if(t <= 2) { 46 puts("-1"); 47 return 0; 48 } 49 for(int i = 3; i <= sqrt(t); i++) { 50 if(t % i == 0) { 51 LL tmp = t / i; 52 LL x = 1LL * i * i; 53 if(x & 1) { 54 printf("%lld %lld\n", (1LL * i * i - 1) / 2 * tmp, (1LL * i * i + 1) / 2 * tmp); 55 return 0; 56 } 57 } 58 } 59 LL num = 1; 60 while(t % 2 == 0) { 61 num = num * 2; 62 t /= 2; 63 } 64 if(t == 1) { 65 t = 4; 66 num /= 4; 67 printf("%lld %lld\n", 3 * num, 5 * num); 68 } else { 69 printf("%lld %lld\n", (t * t - 1) / 2 * num, (t * t + 1) / 2 * num); 70 } 71 return 0; 72 }