HDU1540 Turnal Warfare

线段树保存每个区间的左边最大连续长度和右边最大连续长度~

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<string>
using namespace std;
const int maxn=1e6+14;
struct node {
    int l,r;
    int ll,rl,ml;
    //左边开始连续的最大长度和右边开始连续的最大长度
    //以及这个区间的最大连续长度 
}segTree[maxn*4];
void build (int i,int l,int r) {
    segTree[i].l=l;
    segTree[i].r=r;
    segTree[i].ll=segTree[i].rl=segTree[i].ml=r-l+1;
    if (l==r) return;
    int mid=(l+r)>>1;
    build (i<<1,l,mid);
    build (i<<1|1,mid+1,r);
}
void update (int i,int t,int val) {
    if (segTree[i].l==segTree[i].r) {
        if (val==1) segTree[i].ll=segTree[i].rl=segTree[i].ml=1;
        else segTree[i].ll=segTree[i].rl=segTree[i].ml=0;
        return;
    }
    int mid=(segTree[i].l+segTree[i].r)>>1;
    if (t<=mid) update (i<<1,t,val);
    else update (i<<1|1,t,val);
    segTree[i].ll=segTree[i<<1].ll;
    segTree[i].rl=segTree[i<<1|1].rl;
    segTree[i].ml=max(segTree[i<<1].ml,segTree[i<<1|1].ml);
    segTree[i].ml=max(segTree[i].ml,segTree[i<<1].rl+segTree[i<<1|1].ll);
    if (segTree[i<<1].ll==segTree[i<<1].r-segTree[i<<1].l+1) segTree[i].ll+=segTree[i<<1|1].ll;
    if (segTree[i<<1|1].rl==segTree[i<<1|1].r-segTree[i<<1|1].l+1)
    segTree[i].rl+=segTree[i<<1].rl;
}
int query (int i,int t) {
    if (segTree[i].l==segTree[i].r||segTree[i].ml==0||segTree[i].ml==segTree[i].r-segTree[i].l+1)
    return segTree[i].ml;
    int mid=(segTree[i].l+segTree[i].r)>>1;
    if (t<=mid) {
        if (t>=segTree[i<<1].r-segTree[i<<1].rl+1)
        return query (i<<1,t)+query (i<<1|1,mid+1);
        else return query (i<<1,t);
    } 
    else {
        if (t<=segTree[i<<1|1].l+segTree[i<<1|1].ll-1)
        return query (i<<1|1,t)+query(i<<1,mid);
        else return query (i<<1|1,t);
    }
}
int a[maxn],top,n,m,x;
string s;
int main () {
    while (~scanf ("%d %d",&n,&m)) {
        build (1,1,n);
        top=0;
        while (m--) {
            cin>>s;
            if (s=="D") {
                scanf ("%d",&x);
                a[top++]=x;
                update (1,x,0);
            }
            else if (s=="Q") {
                scanf ("%d",&x);
                printf ("%d\n",query(1,x));
            }
            else {
                if (x>0) {
                    x=a[--top];
                    update (1,x,1);
                }
            }
        }
    }
    return 0;
}