Lightoj 1038 概率DP

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <iostream>
#include<functional>
#include <queue>
#include <string>
#include <algorithm>
using namespace std;
const int maxn = 100005;
const int inf = 1<<30;
const double eps = 1e-7;
int n;
double dp[maxn];
void init()
{
dp[1] = 0;
for( int i = 2; i <= 100000; i ++ ){
double sum = 0;
int cnt = 0;
for( int j = 1; j*j <= i; j ++ ){
if( i%j == 0 ){
sum += dp[j];
cnt ++;
if( j != i/j ){
sum += dp[i/j];
cnt ++;
}
}
}
dp[i] = ( sum + cnt )/( cnt - 1 );
}
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("data.txt","r",stdin);
#endif
init();
int cas,c = 1;
scanf("%d",&cas);
while( cas -- )
{
scanf("%d",&n);
printf("Case %d: %lf\n",c++,dp
);
}
return 0;
}

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <iostream>
#include<functional>
#include <queue>
#include <string>
#include <algorithm>
using namespace std;
const int maxn = 100005;
const int inf = 1<<30;
const double eps = 1e-7;
int n;
struct Edge
{
int to, next;
}edge[maxn*20];

double dp[maxn];
int E,head[maxn];

void add_edge( int u, int to )
{
edge[E].to = to;
edge[E].next = head[u];
head[u] = E++;
}

void init()
{
E = 0;
memset( head, -1, sizeof(head) );
for ( int i = 0; i < maxn; i ++ ) dp[i] = 0.0;
for ( int x = 100000; x >= 2; x -- ){
for (int i = 2; i * i <= x; i ++ ){
if (x % i == 0){
add_edge(x, i);
if( x / i != i )
add_edge(x, x/i);
}
}
}
}

double dfs( int u )
{
if( dp[u] >= eps ) return dp[u];
if( u == 1 ) return 0.0;
double sum = 2;
int cnt = 2;
for( int i = head[u]; i != -1; i = edge[i].next ){
cnt++;
sum += dfs(edge[i].to) + 1;
}
return dp[u] = sum / (cnt-1);
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("data.txt","r",stdin);
#endif
init();
int cas,c = 1;
scanf("%d",&cas);
while( cas -- )
{
scanf("%d",&n);
printf("Case %d: %f\n",c++,dfs(n));
}
return 0;
}