hdu 1540 Tunnel Warfare 线段树 区间合并

#include <bits/stdc++.h>
#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1
using namespace std;

const int MAXN = 55555;
int mx[MAXN<<2], lmx[MAXN<<2], rmx[MAXN<<2];
int des[MAXN];

void push_up(int rt, int len)
{
    lmx[rt] = lmx[rt<<1];
    rmx[rt] = rmx[rt<<1|1];
    if(lmx[rt] == len - (len >> 1)) lmx[rt] += lmx[rt<<1|1];
    if(rmx[rt] == len >> 1)  rmx[rt] += rmx[rt<<1];
    mx[rt] = max(rmx[rt<<1] + lmx[rt<<1|1], max(mx[rt<<1], mx[rt<<1|1]));
}

void build(int l, int r, int rt)
{
    mx[rt] = lmx[rt] = rmx[rt] = r - l + 1;
    if(l == r) return;
    int m = (l + r) >> 1;
    build(lson);
    build(rson);
}

void update(int p, int c, int l, int r, int rt)
{
    if(l == r)
    {
        mx[rt] = c;
        lmx[rt] = c;
        rmx[rt] = c;
        return;
    }
    int m = (l + r) >> 1;
    if(p <= m) update(p, c, lson);
    else update(p, c, rson);
    push_up(rt, r-l+1);
}

int query(int p, int l, int r, int rt)
{
    if(mx[rt] == 0) return 0;
    if(mx[rt] == r - l + 1) return r - l + 1;
    int m = (l + r) >> 1;
    if(p > m - rmx[rt<<1] && p <= m + lmx[rt<<1|1])
        return rmx[rt<<1] + lmx[rt<<1|1];
    if(p <= m) return query(p, lson);
    return query(p, rson);
}

int main()
{
//    freopen("in.txt", "r", stdin);
    int n, m;
    while(~scanf("%d%d", &n, &m))
    {
        build(1, n, 1);
        int cnt = 0;
        while(m--)
        {
            int x;
            char op[3];
            scanf("%s", op);
            if(op[0] == ‘D‘)
            {
                scanf("%d\n", &x);
                des[cnt++] = x;
                update(x, 0, 1, n, 1);
            }
            else if(op[0] == ‘R‘)
            {
                if(cnt == 0) continue;
                update(des[--cnt], 1, 1, n, 1);
            }
            else
            {
                scanf("%d", &x);
                printf("%d\n", query(x, 1, n, 1));
            }
        }
    }
    return 0;
}