bzoj1935

树状数组+离线

按x排序，y离散化，树状数组查询，跟逆序对一样

#include<bits/stdc++.h>
using namespace std;
const int N = 500010;
int n, m, tot, lim;
vector<int> v;
int ans[N], aa[N], b[N], c[N], d[N], xx[N], yy[N];
map<int, int> mp;
struct BIT {
    int tree[N];
    int lowbit(int i) 
    {
        return i & (-i);
    }
    void update(int pos, int delta)
    {
        for(int i = pos; i <= lim; i += lowbit(i)) tree[i] += delta;
    }
    int query(int pos)
    {
        int ret = 0;
        for(int i = pos; i; i -= lowbit(i)) ret += tree[i];
        return ret;
    }
} t;
struct data {
    int x, y, f, id, type;
    data(int x = 0, int y = 0, int f = 0, int type = 0, int id = 0) : x(x), y(y), f(f), type(type), id(id) {}
    bool friend operator < (data A, data B)
    {
        if(A.x == B.x) return A.type < B.type;
        return A.x < B.x;
    }
} a[N * 5];
int main()
{
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; ++i)
    {
        int x, y;
        scanf("%d%d", &xx[i], &yy[i]);
        v.push_back(yy[i]);
    }
    for(int i = 1; i <= m; ++i)
    {
        scanf("%d%d%d%d", &aa[i], &b[i], &c[i], &d[i]);
        v.push_back(b[i]);
        v.push_back(d[i]);
    }
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    for(int i = 0; i < v.size(); ++i) mp[v[i]] = i + 2;
    lim = v.size() + 1;
    for(int i = 1; i <= n; ++i)
    {
        a[++tot].x = xx[i];
        a[tot].y = mp[yy[i]];
        a[tot].type = 0;
    }
    for(int i = 1; i <= m; ++i)
    {
        a[++tot] = data(c[i], mp[d[i]], 1, 1, i);
        a[++tot] = data(aa[i] - 1, mp[b[i]] - 1, 1, 1, i);
        a[++tot] = data(aa[i] - 1, mp[d[i]], -1, 1, i);
        a[++tot] = data(c[i], mp[b[i]] - 1, -1, 1, i);
    }
    sort(a + 1, a + tot + 1);
    for(int i = 1; i <= tot; ++i)
    {
        if(a[i].type == 0) t.update(a[i].y, 1);
        if(a[i].type == 1) ans[a[i].id] += t.query(a[i].y) * a[i].f; 
    }
    for(int i = 1; i <= m; ++i) printf("%d\n", ans[i]);
    return 0;
}