FZU 2029 买票问题

好久没有做题了，开始做这道题时也不知道是咋想的，竟然有链表去实现，弄了好大时候也没弄出来，最后网上看了一下思路，

豁然开朗，用数组就可以实现，总体来说这题用的知识有map<int,int>映射：把输入的x映射为1,2,3...；还有就是树状数组

求"check x y"的值，再加上一个flag数组标记x是否在队列里边就OK了！具体看代码实现吧…………

#include <iostream>
#include <vector>
#include <queue>
#include <map>
#include <cstring>
#include <algorithm>
#include <cstdio>
using namespace std;
#define N 100005
int n, a[N], num, top;
struct node{
    int x, y;
    node(int x, int y):x(x), y(y){}
    node(){}
};

bool operator < (node a, node b){
    return a.y > b.y;
}

int lowbit(int x){
    return x & (-x);
}

void update(int x, int v){
    while( x <= n ){
        a[x] += v;
        x += lowbit(x);
    }
}

int sum(int x){
    int ans = 0;
    while( x > 0 ){
        ans += a[x];
        x -= lowbit(x);
    }
    return ans;
}

int main()
{
    int t, x, y;
    char ss[8];
    while(~scanf("%d", &t)){
        n = t;
        top = 0, num = 1;
        map<int, int> m;
        bool flag[N];
        priority_queue<node> q;
        memset(a, 0, sizeof(a));
        memset(flag, false, sizeof(flag));
        while(t--){
            scanf("%s", ss);
            if(ss[0] == 'l') {
                while( !q.empty() && !flag[q.top().x] ) q.pop();
                if( !q.empty() ) {
                    int k = q.top().x; q.pop();
                    flag[ k ] = false;
                    update(k, -1);
                }
            }
            else if(ss[0] == 'p') {
                while( top < num && !flag[top] ) top++;
                if( top + 1 > num ) continue;
                update( top, -1 );
                flag[top] = false;
                top++;
            }
            else if( ss[0] == 'a' ){
                scanf("%d%d", &x, &y);
                q.push(node(num, y));
                flag[ m[x] = num ] = true;
                num++;
            }
            else {
                scanf("%d%d", &x, &y);
                x = m[x];
                if( !flag[x] ) continue;
                int yy = x + sum(x-1) - 1;
                printf("%d
", yy);
                if( yy > y ){
                    update( x, -1 );
                    flag[x] = false;
                }
            }
        }
    }
    return 0;
}