UVa 160 Factors and factorials: number theory

160-factors and Factorials

Time limit:3.000 seconds

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=96

Topic Point this: http://uva.onlinejudge.org/external/1/160.pdf

Train of thought: Traversal 1~n calculate the number of qualitative factors.

If you want to be faster, use [n/p]+[n/p^2]+[n/p^3]+...+1 in O (log n/log p) time to count the number of n! p. (although this question is too small, the two methods are not very different in time)

Complete code:

/*0.016s*/#include <cstdio> #include <cmath> #include <cstring> int prime[100], C, a  
NS[100];  
    
BOOL vis[110];  
    inline void Create_prime () {int i, J;  
            for (i = 2; I <= ++i) if (!vis[i]) {prime[c++] = i;  
        for (j = i * I; J < A; J + = i) vis[j] = true;  
for (; i < A; ++i) if (!vis[i]) prime[c++] = i;  
    int main (void) {create_prime ();  
    int n, temp;  
        while (scanf ("%d", &n), N) {memset (ans, 0, sizeof (ans)); printf ("%3d!  
        = ", n);  
            for (int i = 2; I <= n; i++) {temp = i;  
                for (int j = 0; J < c && Prime[j] <= i; j +) {while (temp% prime[j] = 0)  
                    {++ans[prime[j]];  
                Temp/= prime[j];  }
            for (int i = 0, j = 0; Prime[i] <= N; i++, J + +) {if J%  
            (= = = 0 && j) printf ("\ n");  
        printf ("%3d", Ans[prime[i]);  
    } putchar (' \ n ');  
return 0; }

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