线段树的区间合并 B - LCIS

B - LCIS

HDU - 3308

这个是一个很简单很明显的线段树的区间合并，不过区间合并的题目都还是有点难写，建议存个板子。

#include <cstdio>

#include <cstdlib>

#include <algorithm>

#include <iostream>

#define inf 0x3f3f3f3f

using namespace std;

const int maxn = 1e5 + ;

struct node

{

    int l, r, rp, lp, len;

    int max_pre, max_sub, max_last;

}tree[maxn*];

int a[maxn];

void push_up(int id)

{

    tree[id].rp = tree[id<<|].rp;

    tree[id].lp = tree[id << ].lp;

    tree[id].max_pre = tree[id << ].max_pre;

    tree[id].max_last = tree[id <<  | ].max_last;

    tree[id].max_sub = max(tree[id << ].max_sub, tree[id <<  | ].max_sub);

    if(tree[id<<].rp<tree[id<<|].lp)

    {

        if (tree[id << ].max_pre == tree[id << ].len) tree[id].max_pre += tree[id <<  | ].max_pre;

        if (tree[id <<  | ].max_last == tree[id <<  | ].len) tree[id].max_last += tree[id << ].max_last;

        tree[id].max_sub = max(tree[id].max_sub, tree[id << ].max_last + tree[id<<|].max_pre);

    }

}

void build(int id,int l,int r)

{

    tree[id].l = l;

    tree[id].r = r;

    tree[id].len = r - l + ;

    if(l==r)

    {

        tree[id].rp = tree[id].lp = a[l];

        tree[id].max_pre = tree[id].max_last = tree[id].max_sub = ;

        return;

    }

    int mid = (l+r) >> ;

    build(id << , l, mid);

    build(id <<  | , mid + , r);

    push_up(id);

}

int query(int id,int x,int y)

{

    int ans = ;

    if(x<=tree[id].l&&tree[id].r<=y)

    {

        return tree[id].max_sub;

    }

    int mid = (tree[id].l + tree[id].r) >> ;

    if (x <= mid) ans = max(ans, query(id << , x, y));

    if (y > mid) ans = max(ans, query(id <<  | , x, y));

    if(tree[id<<].rp<tree[id<<|].lp)

    {

        ans = max(ans, min(mid - x + , tree[id << ].max_last) + min(y - mid, tree[id <<  | ].max_pre));

    }

    return ans;

}

void update(int id,int x,int z)

{

    if(tree[id].l==tree[id].r&&tree[id].l==x)

    {

        tree[id].rp = z;

        tree[id].lp = z;

        return;

    }

    int mid = (tree[id].l + tree[id].r) >> ;

    if (x <= mid) update(id << , x, z);

    if (x > mid) update(id <<  | , x, z);

    push_up(id);

}

int main()

{

    int t;

    scanf("%d", &t);

    while(t--)

    {

        int n, m;

        scanf("%d%d", &n, &m);

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

        {

            scanf("%d", &a[i]);

        }

        build(, , n);

        while(m--)

        {

            char s[];

            int x, y;

            scanf("%s %d %d", s, &x, &y);

            if(s[]=='Q')

            {

                int ans = query(, x+, y+);

                printf("%d\n", ans);

            }

            else update(, x+, y);

        }

    }

}