hdu 5104 Primes Problem

题目连接

http://acm.hdu.edu.cn/showproblem.php?pid=5104

Primes Problem

Description

Given a number n, please count how many tuple$(p_1, p_2, p_3)$ satisfied that $p_1 \leq p_2  \leq p_3, $ $p_1,p_2,p_3$ are primes and $p_1 + p_2 + p_3 = n$.

Input

Multiple test cases(less than 100), for each test case, the only line indicates the positive integer $n\ (n \leq 10000).$

Output

For each test case, print the number of ways.

Sample Input

3
9

Sample Output

0
2

简单题如下。。

 #include<algorithm>
 #include<iostream>
 #include<cstdlib>
 #include<cstring>
 #include<cstdio>
 #include<vector>
 #include<map>
 #include<set>
 using std::cin;
 using std::cout;
 using std::endl;
 using std::find;
 using std::sort;
 using std::set;
 using std::map;
 using std::pair;
 using std::vector;
 using std::multiset;
 using std::multimap;
 #define pb(e) push_back(e)
 #define sz(c) (int)(c).size()
 #define mp(a, b) make_pair(a, b)
 #define all(c) (c).begin(), (c).end()
 #define iter(c) decltype((c).begin())
 #define cls(arr,val) memset(arr,val,sizeof(arr))
 #define cpresent(c, e) (find(all(c), (e)) != (c).end())
 #define rep(i, n) for (int i = 0; i < (int)(n); i++)
 #define tr(c, i) for (iter(c) i = (c).begin(); i != (c).end(); ++i)
 const int N = ;
 typedef unsigned long long ull;
 bool P[N];
 int tot, prime[];
 bool isPrim(int n) {
     for (int i = ; i * i <= n; i++) if (n % i == ) return false;
     return n != ;
 }
 inline void init() {
     for (int i = ; i < N;i++) {
         if (isPrim(i)) prime[tot++] = i, P[i] = true;
         else P[i] = false;
     }
 }
 inline void solve(int n) {
     int res = ;
     for (int i = ; i < tot && prime[i] < n; i++) {
         for (int j = i; j < tot && prime[j] < n; j++) {
             int t = n - prime[i] - prime[j];
             if (t >= prime[j] && P[t]) res++;
         }
     }
     printf("%d\n", res);
 }
 int main() {
 #ifdef LOCAL
     freopen("in.txt", "r", stdin);
     freopen("out.txt", "w+", stdout);
 #endif
     int n;
     init();
     while (~scanf("%d", &n)) {
         solve(n);
     }
     return ;
 }