poj1442

树状数组

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

#define maxn 30005

struct Elem
{
    int a;
    int id;
} elem[maxn];

int n, m;
int pos[maxn];
int get[maxn];
int ar[maxn];

int lowb(int t)
{
    return t & (-t);
}

void add(int i, int v)
{
    for (; i < maxn; ar[i] += v, i += lowb(i))
        ;
}

int sum(int i)
{
    int s = 0;
    for (; i > 0; s += ar[i], i -= lowb(i))
        ;
    return s;
}

bool operator <(const Elem &a, const Elem &b)
{
    return a.a < b.a;
}

void input()
{
    scanf("%d%d", &m, &n);
    for (int i = 0; i < m; i++)
    {
        scanf("%d", &elem[i].a);
        elem[i].id = i;
    }
    for (int i = 0; i < n; i++)
        scanf("%d", &get[i]);
}

bool ok(int x, int a)
{
    return sum(x) >= a;
}

int binarysearch(int a)
{
    int l = 1;
    int r = m;
    while (l < r)
    {
        int mid = (l + r) / 2;
        if (ok(mid, a))
            r = mid;
        else
            l = mid + 1;
    }
    return l;
}

void work()
{
    for (int i = 0; i < m; i++)
        pos[elem[i].id] = i + 1;
    int s = 0;
    int x = 0;
    for (int i = 0; i < n; i++)
    {
        for (int j = s; j < get[i]; j++)
            add(pos[j], 1);
        s = get[i];
        x++;
        printf("%d\n", elem[binarysearch(x) - 1].a);
    }
}

int main()
{
    //freopen("t.txt", "r", stdin);
    input();
    sort(elem, elem + m);
    work();
    return 0;
}