Hdu1540Tunnel Warfare线段树

　　直接搞吧，就是用栈存复原点时要判下栈顶指针是否空。不然会wa在Hdu上。ps：打日本鬼子的题，必须ac啊

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <climits>
#include <string>
#include <iostream>
#include <map>
#include <cstdlib>
#include <list>
#include <set>
#include <queue>
#include <stack>
#include<math.h>
using namespace std;
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
const int maxn = 55555;
int sum[maxn << 2];
int lsum[maxn << 2];
int rsum[maxn << 2];
void up(int rt, int m)
{
    lsum[rt] = lsum[rt << 1];
    rsum[rt] = rsum[rt << 1 | 1];
    if (lsum[rt] == (m - (m >> 1))) lsum[rt] += lsum[rt << 1 | 1];
    if (rsum[rt] == (m >> 1)) rsum[rt] += rsum[rt << 1];
    sum[rt] = max(max(sum[rt << 1], sum[rt << 1 | 1]), rsum[rt << 1] + lsum[rt << 1 | 1]);
}

void build(int l, int r, int rt)
{
    if (l == r){
        sum[rt] = lsum[rt] = rsum[rt] = 1;
        return;
    }
    int mid = (l + r) >> 1;
    build(lson);
    build(rson);
    up(rt, r - l + 1);
}

void update(int key, int add, int l, int r, int rt)
{
    if (l == r){
        if (add) sum[rt] = lsum[rt] = rsum[rt] = 0;
        if (!add) sum[rt] = lsum[rt] = rsum[rt] = 1;
        return;
    }
    int mid = (l + r) >> 1;
    if (key <= mid) update(key, add, lson);
    else update(key, add, rson);
    up(rt, r - l + 1);
}

int ask(int key, int l, int r, int rt)
{
    if (l == r){
        if (sum[rt] == 1) return 1; return 0;
    }
    int mid = (l + r) >> 1;
    int a = l + lsum[rt] - 1; int b = r - rsum[rt] + 1;
    int ans = 0;
    if (key >= l&&key <= a) ans = lsum[rt];
    if (key >= b&&key <= r) ans = max(ans, rsum[rt]);
    int c = mid - rsum[rt << 1] + 1; int d = lsum[rt << 1 | 1] + mid;
    if (key >= c&&key <= d) ans = max(ans, rsum[rt << 1] + lsum[rt << 1 | 1]);
    if (ans) return ans;
    if (key <= mid) return ask(key, lson);
    else return ask(key, rson);
}
int q[maxn<<1];
int main()
{
    int n, m;
    int a; char str[100];
    while (scanf("%d%d",&n,&m)!=EOF){
        build(1, n, 1);
        int ans = 0;
        for (int i = 0; i < m; i++){
            scanf("%s%d", str, &a);
            if (str[0] == 'D'){
                update(a, 1, 1, n, 1);
                q[ans++] = a;
            }
            if (str[0] == 'Q'){
                printf("%d
", ask(a, 1, n, 1));
            }
            if (str[0] == 'R'){
                if(ans<=0) continue;
                int t = q[--ans];
                update(t, 0, 1, n, 1);
            }
        }
    }
    return 0;
}