树状数组练习 POJ-2481

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/qq_30986521/article/details/82689058

题目链接 

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>

using namespace std;

struct node
{
    int l, r;
    int id;
    friend bool  operator < (node x, node y)
    {
        if (x.r == y.r)
        {
            return x.l < y.l;
        }
        return x.r > y.r;
    }
};

#define N 100010

int t[N];
node a[N];
int ans[N];

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

int getsum(int k)
{
    int sum = 0;
    while (k)
    {
        sum += t[k];
        k -= lowbit(k);
    }
    return sum;
}

void update(int k, int delta)
{
    while (k < N)
    {
        t[k] += delta;
        k += lowbit(k);
    }
}

int main()
{
    int n;
    
    while (scanf("%d", &n) && n != 0)
    {
        memset(t, 0, sizeof(t));
        memset(a, 0, sizeof(a));
        memset(ans, 0, sizeof(ans));
        for (int i = 1; i <= n; i++)
        {
            scanf("%d%d", &a[i].l, &a[i].r);
            a[i].l++;
            a[i].r++;
            a[i].id = i;
        }
        
        sort(a + 1, a + 1 + n);
        
        node pre;
        pre.l = pre.r = pre.id;
        for (int i = 1; i <= n; i++)
        {
            if (pre.l == a[i].l && pre.r == a[i].r)
            {
                ans[a[i].id] = ans[pre.id];
                update(a[i].l, 1);
            }
            else
            {
                ans[a[i].id] = getsum(a[i].l);
                update(a[i].l, 1);
            }
            pre = a[i];
        }
        
        for (int i = 1; i <= n; i++)
        {
            printf("%d ", ans[i]);
        }
        putchar(10);
    }
    return 0;
}