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\n", 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;

}