使用大数的基础dp

https://vj.xtuacm.cf/contest/view.action?cid=63#problem/I
Dollar Dayz

Description
Farmer John goes to Dollar Days at The Cow Store and discovers an unlimited number of tools on sale. During his first visit, the tools are selling variously for 1,2, and 3.FarmerJohnhasexactly5 to spend. He can buy 5 tools at 1eachor1toolat3 and an additional 1 tool at $2. Of course, there are other combinations for a total of 5 different ways FJ can spend all his money on tools. Here they are:

    1 @ US$3 + 1 @ US$2 

1 @ US3+2@US1
1 @ US2+3@US1
2 @ US2+1@US1
5 @ US$1

Write a program than will compute the number of ways FJ can spend N dollars (1 <= N <= 1000) at The Cow Store for tools on sale with a cost of 1..K (1 <= K <= 100).

Input
A single line with two space-separated integers: N and K.

Output
A single line with a single integer that is the number of unique ways FJ can spend his money.

Sample Input

5 3

Sample Output

5

• 题解：注意大数的使用方法 以及将二维状态方程变成一维

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#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>using namespace std;const int maxn=1005;long long a[maxn],b[maxn];long long inf=1e18;int main(){    int n,k;    scanf("%d%d",&n,&k);    memset(a,0,sizeof(a));    memset(b,0,sizeof(b));    a[0]=1;    // cout<<inf<<endl;011    for(int i=1; i<=k; i++)        for(int j=1; j<=n; j++)        {            if(j<i)continue;            b[j]=b[j]+b[j-i]+(a[j]+a[j-i])/inf;            a[j]=(a[j]+a[j-i])%inf;//***注意这一行和上一行位置不能互换，如果这一句在前a[j]就会被赋值两次***        }    if(b[n])        printf("%I64d",b[n]);    printf("%I64d\n",a[n]);    return 0;}