Ultraviolet A 10869-Brownie points II (tree array)

Link: Ultraviolet A 10869-Brownie points II

Given a number of points, the first person selects the abscissa of an existing point, and the second person selects a point on the abscissa to create a coordinate system using this point as the origin, 1. The three Elephant points belong to the first person, the second and fourth quadrants belong to the second person, and the coordinate axes do not belong to anyone. Ask how many points a second person may obtain when the first person gets the most points.

Solution: Sort all vertices in ascending order of X coordinates and Y coordinates in ascending order, in this way, the number of vertices in the upper right corner of each vertex can be processed from left to right (maintained using a tree array), and the points in the lower left corner can be obtained from right to left.

#include <cstdio>#include <cstring>#include <set>#include <algorithm>#define lowbit(x) ((x)&(-x))using namespace std;const int maxn = 200000;set<int> vec;int ans;int N, R, C, fenx[maxn+5], rec[maxn+5];int cntx[maxn+5], cnty[maxn+5], have[maxn+5];struct point {    int x, y;    int rx, ry;}p[maxn+5];inline bool sort_y (const point& a, const point& b) {    return a.y < b.y;}inline bool sort_xby (const point& a, const point& b) {    if (a.x != b.x)        return a.x < b.x;    return a.y > b.y;}inline bool sort_xsy (const point& a, const point& b) {    if (a.x != b.x)        return a.x > b.x;    return a.y < b.y;}void add_treeArr (int x, int val) {    while (x <= maxn) {        fenx[x] += val;        x += lowbit(x);    }}int query_treeArr (int x) {    int ret = 0;    while (x) {        ret += fenx[x];        x -= lowbit(x);    }    return ret;}void init () {    memset(cntx, 0, sizeof(cntx));    memset(cnty, 0, sizeof(cnty));    memset(fenx, 0, sizeof(fenx));    for (int i = 0; i < N; i++)        scanf("%d%d", &p[i].x, &p[i].y);    sort(p, p + N, sort_y);    C = p[0].ry = 1;    add_treeArr(C, 1);    for (int i = 1; i < N; i++) {        if (p[i].y != p[i-1].y)            C++;        p[i].ry = C;        add_treeArr(C, 1);    }    sort(p, p + N, sort_xby);    R = p[0].rx = 0;    for (int i = 1; i < N; i++) {        if (p[i].x != p[i-1].x)            R++;        p[i].rx = R;    }}void set_ans (int ret, set<int> v) {    if (ret > ans) {        ans = ret;        vec.clear();    }    if (ret == ans) {        for (set<int>::iterator i = v.begin(); i != v.end(); i++)            vec.insert(N - ret - cntx[p[*i].rx] - cnty[p[*i].ry] + 1);    }}void solve () {    memcpy(rec, fenx, sizeof(fenx));    for (int i = 0; i < N; i++) {        have[i] = query_treeArr(C) - query_treeArr(p[i].ry);        add_treeArr(p[i].ry, -1);        cntx[p[i].rx]++;        cnty[p[i].ry]++;    }    ans = 0;    vec.clear();    memcpy(fenx, rec, sizeof(rec));    int pre = p[N-1].rx, ret = N;    set<int> oll;    for (int i = N-1; i >= 0; i--) {        int tmp = have[i] + query_treeArr(p[i].ry - 1);        add_treeArr(p[i].ry, -1);        if (p[i].rx != pre) {            set_ans(ret, oll);            pre = p[i].rx;            ret = N;            oll.clear();        }        if (ret > tmp) {            ret = tmp;            oll.clear();        }        if (ret == tmp)            oll.insert(i);    }    set_ans(ret, oll);    printf("Stan: %d; Ollie:", ans);    for (set<int>::iterator i = vec.begin(); i != vec.end(); i++)        printf(" %d", *i);    printf(";\n");}int main () {    while (scanf("%d", &N) == 1 && N) {        init();        solve();    }    return 0;}

Ultraviolet A 10869-Brownie points II (tree array)