hdu 3450 Counting Sequences(树状数组)

和前面一题差不多的思路。但是这题要做的处理多一点。

题意:相邻两个数之和<=d.给出一个序列计算出符合要求的序列个数。

abs(a[i]-a[j])<=d

d-a[i]<=a[j]<=d+a[i]

找到大于a[i]-d的最大数L,

找到小于a[i]+d的最大数R

求出[L,R]之间小于等于H的数。

/*
Problem ID:
meaning:
Analyzing:
*/
#include <iostream>
#include <algorithm>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<vector>

using namespace std;
typedef struct even{int y1,y2,x;}even;

#define clr(A,k) memset(A,k,sizeof(A))
#define FOR(i,s,t) for(int i=(s); i<(t); i++)
#define LL long long
#define BUG puts("here!!!")
#define print(x) printf("%d\n",x)
#define STOP system("pause")
#define eps 1e-8
#define PI acos(-1.0)
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define maxn 100006
#define maxm 1005
#define MOD   9901
#define lowbit(x) x&(-x)
LL gcd(LL a,LL b) {return a?gcd(b%a,a):b;}
int n,d,len;
int C[maxn],A[maxn],S[maxn];
void update(int pos,int val){
    while(pos<=len){
        C[pos]+=val;
        if(C[pos]>=MOD) C[pos]%=MOD;
        pos+=lowbit(pos);
    }
}
int query(int x){
    int sum=0;
    while(x>0){
        sum+=C[x];
        if(sum>=MOD) sum%=MOD;
        x-=lowbit(x);
    }
    return sum;
}
int BinLeft(int left){
    int l=1,r=len,ans=0;
    while(l<=r){
        int m=(l+r)>>1;
        if(S[m]>=left){
            ans=m;
            r=m-1;
        }
        else {
            l=m+1;
        }
    }
    return ans;
}

int BinRight(int right){
    int l=1,r=len,ans=len;
    while(l<=r){
        int m=(l+r)>>1;
        if(S[m]<=right){
            ans=m;
            l=m+1;
        }
        else {
            r=m-1;
        }
    }
    return ans;
}

int BinSearch(int x){
    int l=1,r=len;
    while(l<=r){
        int m=(l+r)>>1;
        if(S[m]==x) return m;
        if(S[m]>x) r=m-1;
        else l=m+1;
    }
}

int main(){
    int n;
    while(~scanf("%d%d",&n,&d)){
        for(int i=1;i<=n;i++){
            scanf("%d",&A[i]);
            S[i]=A[i];
        }
        sort(S+1,S+n+1);
        len=2;
        for(int i=2;i<=n;i++){
            if(S[i]!=S[i-1])
            S[len++]=S[i];
        }
        clr(C,0);
        int  sum=0;
        for(int i=1;i<=n;i++){
            int id=BinSearch(A[i]);
           // cout<<"ID :"<<id<<endl;
            int left=BinLeft(A[i]-d);//找到比A[i]-d大的最小数
           // cout<<"left:"<<left<<endl;
            int right=BinRight(A[i]+d);
            LL tmp=query(right)-query(left-1);
           // cout<<"tmp : "<<tmp<<endl;
            if(tmp<0) tmp+=MOD;
            if(tmp>=MOD) tmp%=MOD;
            sum+=tmp+1;
            if(sum>=MOD) sum%=MOD;
            update(id,tmp+1);
        }
        sum=((sum-n)%MOD+MOD)%MOD;
        printf("%d\n",sum);
    }
return 0;
}