Codeforces 97b superset plane governance

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Question:

Given a Point Set

Add some points before gathering them.

After adding a vertex, any two vertices in the vertex set must satisfy at least one of the following two vertices.

1. On the same horizontal line or on the same vertical line

2. There are other points in the enclosed matrix.

Ideas:

Plane governance

First, sort the points by the X axis, find the center point, and create a straight line x = A [Mid]. X;

Then all vertices are projected onto this line, so the left vertices do not need to be matched with the right.

#pragma comment(linker, "/STACK:1024000000,1024000000")#include <stdio.h>#include <algorithm>#include <iostream>#include <set>#include <queue>#include <cstring>using namespace std;typedef long long ll;typedef pair<int,int> pii;const int inf = 1e9;template <class T>inline bool rd(T &ret) {    char c; int sgn;    if(c=getchar(),c==EOF) return 0;    while(c!='-'&&(c<'0'||c>'9')) c=getchar();    sgn=(c=='-')?-1:1;    ret=(c=='-')?0:(c-'0');    while(c=getchar(),c>='0'&&c<='9') ret=ret*10+(c-'0');    ret*=sgn;    return 1;}template <class T>inline void pt(T x) {    if (x <0) {        putchar('-');        x = -x;    }    if(x>9) pt(x/10);    putchar(x%10+'0');}#define N 10005pii a[N], b[N*20];int top, n;void dfs(int l, int r){    int mid = (l+r)>>1, maxx = a[mid].first;    for(int i = l; i <= r; i++)        b[top++] = pii(maxx, a[i].second);    if(l < mid)        dfs(l, mid-1);    if(mid < r)        dfs(mid+1, r);}void input(){    for(int i = 1; i <= n; i++) rd(a[i].first), rd(a[i].second);    sort(a+1, a+1+n);    top = 0;}void output(){    sort(b, b+top);    top = unique(b, b+top)-b;    pt(top); putchar('\n');    for(int i = 0; i < top; i++)        pt(b[i].first), putchar(' '), pt(b[i].second), putchar('\n');}int main(){    while(rd(n)){        input();        dfs(1, n);        output();    }    return 0;}

Codeforces 97b superset plane governance