Educational Codeforces Round 87 (Rated for Div. 2) D

题解

树状数组维护 1 ~ i 在队列中的数量的前缀和

二分查找位置进行增改

#include <bits/stdc++.h>
#define all(n) (n).begin(), (n).end()
#define se second
#define fi first
#define pb push_back
#define mp make_pair
#define sqr(n) (n)*(n)
#define rep(i,a,b) for(int i=a;i<=b;++i)
#define per(i,a,b) for(int i=a;i>=b;--i)
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef double db;

const int N = 1048576 + 5;

int n, m, _, k;
int c[N];

void add(int x, int k)
{
    for (; x <= N; x += -x & x) c[x] += k;
}

int ask(int x)
{
    int ans = 0;
    for (; x; x -= -x & x) ans += c[x];
    return ans;
}

int bfind(int t)
{
    int l = 1, r = N;
    bool flag = 0;
    while (l < r)
    {
        int m = (l + r) >> 1;
        if (ask(m) >= t) r = m, flag = 1;
        else l = m + 1; 
    }
    if (flag) return l;
    return 0;
}

int main()
{
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> n >> m;
    rep (i, 1, n) cin >> k, add(k, 1);
    
    rep (i, 1, m)
    {
        cin >> k;
        if (k > 0) { add(k, 1); continue; }
        add(bfind(-k), -1);
    }
    cout << bfind(1);
    return 0;
}