【HDOJ】1540 Tunnel Warfare

还不错的一道线段树区间合并。挺巧妙的用法。

/* 1540 */
#include <iostream>
#include <string>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <deque>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <climits>
#include <cctype>
#include <cassert>
#include <functional>
#include <iterator>
#include <iomanip>
using namespace std;
//#pragma comment(linker,"/STACK:102400000,1024000")

#define sti                set<int>
#define stpii            set<pair<int, int> >
#define mpii            map<int,int>
#define vi                vector<int>
#define pii                pair<int,int>
#define vpii            vector<pair<int,int> >
#define rep(i, a, n)     for (int i=a;i<n;++i)
#define per(i, a, n)     for (int i=n-1;i>=a;--i)
#define clr                clear
#define pb                 push_back
#define mp                 make_pair
#define fir                first
#define sec                second
#define all(x)             (x).begin(),(x).end()
#define SZ(x)             ((int)(x).size())
#define lson            l, mid, rt<<1
#define rson            mid+1, r, rt<<1|1

const int maxn = 50005;
int ls[maxn<<2], rs[maxn<<2], ms[maxn<<2];
int S[maxn], top;

void Build(int l, int r, int rt) {
    ls[rt] = rs[rt] = ms[rt] = r - l + 1;
    if (l == r)
        return ;
    
    int mid = (l + r) >> 1;
    Build(lson);
    Build(rson);
}

void PushUp(int l, int r, int rt) {
    int mid = (l + r) >>1;
    int lb = rt<<1;
    int rb = lb |1;
    
    ls[rt] = ls[lb];
    rs[rt] = rs[rb];
    if (ls[lb] == mid-l+1)
        ls[rt] += ls[rb];
    if (rs[rb] == r-mid)
        rs[rt] += rs[lb];
    
    ms[rt] = max(ms[lb], ms[rb]);
    ms[rt] = max(ms[rt], rs[lb]+ls[rb]);
}

void update(int x, int delta, int l, int r, int rt) {
    if (l == r) {
        ls[rt] = rs[rt] = ms[rt] = delta;
        return ;
    }
    
    int mid = (l + r) >> 1;
    
    if (x <= mid) {
        update(x, delta, lson);
    } else {
        update(x, delta, rson);
    }
    
    PushUp(l, r, rt);
}

int Query(int x, int l, int r, int rt) {
    if (l==r || ms[rt]==0 || ms[rt]==r-l+1)
        return ms[rt];
    
    int mid = (l + r) >> 1;
    int lb = rt<<1;
    int rb = lb |1;
    
    if (x <= mid) {
        if (x >= mid-rs[lb]+1) {
            return Query(x, lson) + Query(mid+1, rson);
        } else {
            return Query(x, lson);
        }
    } else {
        if (x <= mid+ls[rb]) {
            return Query(mid, lson) + Query(x, rson);
        } else {
            return Query(x, rson);
        }
    }
}

int main() {
    ios::sync_with_stdio(false);
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif
    
    int n, m, x;
    char cmd[5];
    int ans;
    
    while (scanf("%d %d", &n, &m)!=EOF) {
        Build(1, n, 1);
        top = 0;
        while (m--) {
            scanf("%s", cmd);
            if (cmd[0] == 'D') {
                scanf("%d", &x);
                S[top++] = x;
                update(x, 0, 1, n, 1);
            } else if (cmd[0] == 'Q') {
                scanf("%d", &x);
                ans = Query(x, 1, n, 1);
                printf("%d
", ans);
            } else {
                if (top > 0) {
                    x = S[--top];
                    update(x, 1, 1, n, 1);
                }
            }
        }
    }
    
    #ifndef ONLINE_JUDGE
        printf("time = %d.
", (int)clock());
    #endif
    
    return 0;
}