hdu 3450 Counting Sequences(樹狀數組)

和前面一題差不多的思路。但是這題要做的處理多一點。

題意:相鄰兩個數之和<=d.給出一個序列計算出符合要求的序列個數。

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

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

找到大於a[i]-d的最大數L,

找到小於a[i]+d的最大數R

求出[L,R]之間小於等於H的數。

/*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大的最小數           // 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;}