HDU 3436--Queue-jumpers （树状数组 or Splay Tree）

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;

const int N = 200005;
int op[N], a[N], b[N], p[N], no[N];
int n, q;

struct BIT {
    int arr[N];
    int n;
    int sum(int p) {
        int ans = 0;
        while (p) {
            ans += arr[p];
            p -= lowbit(p);
        }
        return ans;
    }
    void add(int p, int v) {
        while (p <= n) {
            arr[p] += v;
            p += lowbit(p);
        }
    }
    int find(int k) { //在数组中找第一个大于等于k的位置
        int pos = 0, cnt = 0;
        for (int i = 17; i >= 0; --i) {
            pos += (1<<i);
            if (pos >= n || cnt + arr[pos] >= k) pos -= (1<<i);
            else cnt += arr[pos];
        }
        return pos+1;
    }
    void init(int n) {
        this->n = n;
        memset(arr, 0, sizeof arr);
    }
    int lowbit(int x) {
        return x&-x;
    }
} bit;


int main()
{
    //freopen("in.txt", "r", stdin);
    int T, cas = 0;
    scanf("%d", &T);
    while (T--) {
        printf("Case %d:\n", ++cas);
        scanf("%d%d", &n, &q);
        char ch[10];
        int idx = 0;
        for (int i = 1; i <= q; ++i) {
           scanf("%s%d", ch, &a[i]);
           if (*ch == ‘T‘) op[i] = 1;
           else if (*ch == ‘Q‘) op[i] = 2;
           else op[i] = 3;
           if (op[i] < 3) b[++idx] = a[i];
        }
        b[++idx] = n;
        sort(b+1, b+1+idx);
        n = unique(b+1, b+1+idx) - b - 1;
        bit.init(2*q);
        for (int i = 1; i <= n; ++i) {
            bit.add(q+i, b[i]-b[i-1]);
            no[q+i] = b[i]; // no[i] 数组i处的编号 原编号！！
            p[i] = q+i;     // p[i] 编号为i的位置
        }
        int top = q;
        for (int i = 1; i <= q; ++i) {
            if (op[i] == 1) {
                int x = lower_bound(b+1, b+1+n, a[i]) - b;
                bit.add(p[x], -1);  // 要把x挪到顶端 p[x]位置的数字个数减少一个
                no[p[x]]--;         // x走了 剩下的是x-1
                p[x] = top;         // x的位置变成了top
                bit.add(top, 1);   // top位置有一个数字x +1
                no[top] = a[i];
                top--;
            } else if (op[i] == 2) {
                int x = lower_bound(b+1, b+1+n, a[i]) - b;
                printf("%d\n", bit.sum( p[ x ] ));
            } else {
                int pos = bit.find(a[i]);
                int sp = bit.sum(pos);
                if (sp == a[i]) printf("%d\n", no[pos]);
                else printf("%d\n", no[pos]-(sp-a[i]));
            }
        }
    }
    return 0;
}