PE 014 Longest Collatz sequence

题目链接：https://projecteuler.net/problem=14

记忆化搜索，中间会爆int

代码：#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
map<ll,int> dp;
int dfs(ll now)
{
if(dp.find(now)!=dp.end())
return dp[now];
if(now&1)
{
dp[now]=dfs(now*3LL+1)+1;
}
else
{
dp[now]=dfs(now/2)+1;
}
}
int main()
{
//freopen("in.txt","r",stdin);
//freopen("out.txt","w",stdout);
int mx=0,ans=0;
dp[1]=1;
for(int i=1;i<1000000;i++)
{
dfs(i);
if(dp[i]>mx)
ans=i,mx=dp[i];
}
printf("%d\n",ans);
return 0;
}