hdu 3308 LCIS 线段树

昨天热身赛的简单版：LCIS。昨天那题用树链剖分，不知道哪里写错了，所以水了水这题看看合并、更新方式是否正确，发现没错啊。看来应该是在树链剖分求lca时写错了。。。

 

题目：给出n个数，有两种操作：

　　1.单点修改

　　2.区间询问：最长连续上升子序列

分析：只需要维护五个域就行：lix，rdx，mix，lval，rval。记录当前区间 最左的值lval ,  最右的值rval，必须从左起连续上升序列的长度lix，必须右起下降的长度rdx。合并时注意下即可。

 

 

#include <cstdio>

#include <cstring>

#include <iostream>

#include <algorithm>



using namespace std;



char IN;

bool NEG;

inline void Int(int &x){

    NEG = 0;

    while(!isdigit(IN=getchar()))

        if(IN=='-')NEG = 1;

    x = IN-'0';

    while(isdigit(IN=getchar()))

        x = x*10+IN-'0';

    if(NEG)x = -x;

}



inline void Char(char &x){

    while(!isupper(x=getchar()));

}



/******** program ********************/



const int MAXN = 200105;



int son[MAXN],sz[MAXN],top[MAXN],fa[MAXN],tid[MAXN],dep[MAXN],tim;

bool use[MAXN];

int a[MAXN];



struct segTree{

    int l,r;

    int lval,rval;

    int lix,mix;

    int rdx;

    segTree(){

        l = r = lval = rval = 0;

        lix = mix = 0;

        rdx = 0;

    }

    inline int mid(){

        return (l+r)>>1;

    }

    inline int dis(){

        return r-l+1;

    }

}tree[MAXN<<1];



inline void update(segTree &now,segTree l,segTree r){

    // lix

    if(l.lix==l.dis()&&l.rval<r.lval)

        now.lix = l.lix+r.lix;

    else now.lix = l.lix;



    // mix

    if(l.rval<r.lval)

        now.mix = max(max(l.mix,r.mix),l.rdx+r.lix);

    else now.mix = max(l.mix,r.mix);



    // rdx

    if(r.dis()==r.rdx&&r.lval>l.rval)

        now.rdx = r.rdx+l.rdx;

    else now.rdx = r.rdx;



    now.lval = l.lval;

    now.rval = r.rval;

}



void build(int l,int r,int rt){

    tree[rt].l = l;

    tree[rt].r = r;

    if(l==r){

        tree[rt].lval = tree[rt].rval = a[l];

        tree[rt].lix = tree[rt].mix = 1;

        tree[rt].rdx = 1;

        return;

    }

    int mid = tree[rt].mid();

    build(l,mid,rt<<1);

    build(mid+1,r,rt<<1|1);

    update(tree[rt],tree[rt<<1],tree[rt<<1|1]);

}



void modify(int pos,int val,int rt){

    if(tree[rt].l==tree[rt].r){

        tree[rt].lval = tree[rt].rval = val;

        return;

    }

    int mid = tree[rt].mid();

    if(pos<=mid)modify(pos,val,rt<<1);

    else modify(pos,val,rt<<1|1);

    update(tree[rt],tree[rt<<1],tree[rt<<1|1]);

}



segTree ask(int l,int r,int rt){

    if(l<=tree[rt].l&&tree[rt].r<=r)

        return tree[rt];

    int mid = tree[rt].mid();

    segTree ans;

    if(r<=mid)ans = ask(l,r,rt<<1);

    else if(l>mid)ans = ask(l,r,rt<<1|1);

    else{

        segTree a = ask(l,r,rt<<1);

        segTree b = ask(l,r,rt<<1|1);

        update(ans,a,b);

    }

    update(tree[rt],tree[rt<<1],tree[rt<<1|1]);

    return ans;

}



int main(){



#ifndef ONLINE_JUDGE

    freopen("sum.in","r",stdin);

    //freopen("sum.out","w",stdout);

#endif



    char op;

    int n,m,ncase,x,y;

    Int(ncase);

    while(ncase--){

        Int(n);Int(m);

        for(int i=1;i<=n;i++)

            Int(a[i]);

        build(1,n,1);

        while(m--){

            Char(op);

            Int(x);Int(y);

            if(op=='Q')printf("%d\n",ask(++x,++y,1).mix);

            else modify(++x,y,1);

        }

    }



    return 0;

}