zoj 3149 Breadtree

D - Breadtree
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Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%lld & %llu

Description

Breadtree is a kind of tree that produces bread. At its first year, a breadtree is only a node with a bread of weight 0 on this node which is also called zeronode. Every year after that, the weight of bread on each node of the tree will increase by 1, and another branch with a zeronode will grow at the end of each node. However, there is a limit of branches on each node. That is, when the number of branches of a node reaches the limit, there won‘t be any more branches, but the weight of its bread will still increase. What‘s more, a breadtree remains unchanged when the total weight of bread is larger than 1234567890.

Input

There are two integers N and K on each line. N is a positive integer fit in signed 32-bit integer. K is a non-negative integer fit in signed 32-bit integer. An N equals to 0 signals the end of input, which should not be processed.

Output

Output the total weight of bread on a breadtree with branches limit K in the N-th year in a line for each case.

Sample Input

10000 0
101 1
10 2
1221 128
0 0

Sample Output

9999
5050
221
2147483647



题意:
树上有节点,节点上有面包,节点每天分出一个分支(到达k后不再分),节点上面的面包每天增重1(到达1234567890后不增),给出n天和k,问第n天面包总重。(n、k都为32为整数)

思路:
开始想的是用一个dp[i]表示面包重为 i 的节点个数,一个sum[i]表示其前缀和,然后模拟树的伸张过程,复杂度有点高TLE了。
正确的思路为:dp[i]表示第i年的总重量(可将一开始看做第0年),则dp[0]=0, 在第i年根重 i ,其余子树重量为第(i-1)年..第(i-k)年的重量和,用一个sum[i]维护,然后直接循环就好了,注意k=0的特判就好了。

代码:
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <string>
#include <map>
#include <stack>
#include <vector>
#include <set>
#include <queue>
#pragma comment (linker,"/STACK:102400000,102400000")
#define maxn 100005
#define MAXN 16005
#define mod 1000000000
#define INF 0x3f3f3f3f
#define pi acos(-1.0)
#define eps 1e-6
typedef long long ll;
using namespace std;

ll n,m,k,ans,cnt,tot,flag;
ll dp[maxn],sum[maxn];
ll xx=1234567890;

ll solve()
{
    ll i,j,d,t;
    dp[0]=sum[0]=0;
    for(i=1;i<=n;i++)
    {
        dp[i]=i+sum[i-1]-sum[max(0LL,i-k-1)];
        sum[i]=sum[i-1]+dp[i];
        if(dp[i]>xx) return dp[i];
    }
    return dp[n];
}
int main()
{
    ll i,j,t;
    while(scanf("%lld%lld",&n,&k),n|k)
    {
        n--;
        if(k==0)
        {
            printf("%lld\n",min(n,xx+1));
            continue ;
        }
        ans=solve();
        printf("%lld\n",ans);
    }
    return 0;
}
/*
10000 0
101 1
10 2
1221 128
0 0
*/




zoj 3149 Breadtree

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