P1400 Tower, P1400

P1400 Tower, P1400
Description

There are N (2 <= N <= 600000) blocks of bricks, to build a n-layer Tower, requirement: If brick A is on Brick B, then A cannot be longer than B's Length + D. There are several ways to output the value of mod 1000000009.

Input/Output Format Input Format:

The first line: N, D the second line: N number, indicating the length of each brick.

Output Format:

Number of solutions, output mod 1000000009

Input and Output sample Input example #1:

4 11 2 3 100

Output sample #1:

4

Multiplication principle

 1 #include<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<cmath> 5 #define lli long long int  6 #include<algorithm> 7 using namespace std; 8 const int MAXN=600001; 9 const int mod=1000000009;10 int read(int & n)11 {12     char c='.';int x=0,flag=0;13     while(c<'0'||c>'9')14     {c=getchar();  if(c=='-')flag=1; }15     while(c>='0'&&c<='9')16     {x=x*10+(c-48);c=getchar();}17     if(flag==1)n=-x;else n=x;18 }19 int n,d;20 int a[MAXN];21 lli ans=1;22 int top=1;23 int maxn=1;24 int main()25 {26     read(n);read(d);27     for(int i=1;i<=n;i++)28         read(a[i]);29     sort(a+1,a+n+1);30     for(int i=2;i<=n;i++)31     {32         while(a[i]>a[top]+d)33         {34             top++;35         }36         ans=ans*(i-top+1);37         ans=ans%mod;38     }39     //printf("%d",ans);40     cout<<ans;41     return 0;42 }