حل سوال 205 ProjectEuler

#include <cmath>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>

using namespace std;

int four9[40];
int six6[40];
int d,l;
int *p;
void dfs(int depth,int sum){
	if(depth == d){
		p[sum]++;return;
	}
	for(int i = 1;i <= l; ++i){
		dfs(depth + 1,sum + i);
	}
}
int main(){
	memset(four9,0,sizeof(four9));
	memset(six6,0,sizeof(six6));
	p = four9;d = 9,l = 4;
	dfs(0,0);
	p = six6;d = 6,l = 6;
	dfs(0,0);
	long long numerator = 0;
	for(int i = 1;i <= 36; ++i) printf("%d ",four9[i]);printf("\n");
	for(int i = 1;i <= 36; ++i) printf("%d ",six6[i]);printf("\n");
	for(int i = 4;i <= 36; ++i){
		for(int j = 6;j <= 36; ++j){
			if(i > j) numerator += 1LL * four9[i] * six6[j];
		}
	}
	printf("%.7f\n",1.0 * numerator / (pow(4.0,9) * pow(6.0,6)));
	return 0;
}

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