小记：真是坑的题目，我以为会有1-999999这样的数据。我用数组标记，每个循环过的数我就记下它的循环次数。下次碰到就直接输出。尼玛爆了RE。用暴力还直接AC了。
思路：暴力吧。我这个RE，大神们帮忙看看。。。
RE的：
#include <iostream>
#include <cstdio>
#include <map>
#include <cstring>
using namespace std;
const int MAX_ = 3000010;
long long d[MAX_];
long long dfs(int x){
if(d[x])return d[x];
if(x == 1)return d[x] = 1;
if(x%2){
return d[x] = dfs(3*x + 1) + 1;
}
else {
return d[x] = dfs(x/2) + 1;
}
}
int main(){
//freopen("f:\\out.txt","w",stdout);
long long n,m, ans, T;
while(cin>>n>>m){
cout<<n<<" "<<m;
if(n > m)swap(n,m);
memset(d,0,sizeof(d));
ans = -1;
for(int i = n; i <= m; ++i){
if(!d[i]){
d[i] = dfs(i);
}
if(ans < d[i])ans = d[i];
}
cout<<" "<<ans<<endl;
}
return 0;
} 暴力的：
#include <iostream>
#include <cstdio>
#include <map>
#include <cstring>
using namespace std;
int df(int x,int n){
if(x == 1)return n;
x = (x%2!=0)?(3*x+1):(x/2);
return df(x,n+1);
}
int main(){
//freopen("f:\\out.txt","w",stdout);
long long n,m, ans, T;
while(cin>>n>>m){
cout<<n<<" "<<m;
if(n > m)swap(n,m);
ans = -1;
for(int i = n; i <= m; ++i){
T = df(i,1);
if(ans < T)ans = T;
}
cout<<" "<<ans<<endl;
}
return 0;
}
