poj 3714 Raid (类型不同点间的最近点对)

#include "stdio.h"
#include "cmath"
#include "iostream"
#include "algorithm"
using namespace std;

struct point
{
long long x, y;
bool flag;
};
point p[200003];
point tp[200003];

bool cmp_x(const point & a, const point & b) { return a.x < b.x; }

bool cmp_y(const point & a, const point & b) { return a.y < b.y; }

double min(double a, double b) { return a < b ? a : b; }

double dis(const point & a, const point & b)
{
if(a.flag == b.flag) return 1e12;  //将类型相同的点之间的距离设为无穷大

return sqrt((double)((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y)));
}

double solve(int lf, int rt, int n)  //left, right
{
if(lf == rt) return 1e12;  //只有一个点时，距离设为无穷大
if(rt - lf == 1)
return dis(p[lf], p[rt]);

int mid = (lf + rt) >> 1;
double ans = min(solve(lf, mid, n), solve(mid + 1, rt, n));

int lp = 0, i, j;
for(i = mid; i >= lf && p[i].x - p[mid].x < ans; i--)
{
tp[lp].x = p[i].x;
tp[lp].y = p[i].y;
tp[lp++].flag = p[i].flag;
}

for(i = mid + 1; i <= rt && p[i].x - p[mid].x < ans; i++)
{
tp[lp].x = p[i].x;
tp[lp].y = p[i].y;
tp[lp++].flag = p[i].flag;
}

sort(tp, tp + lp, cmp_y);

for(i = 0; i < lp; i++)
for(j = i + 1; j - i < 7 && j < lp; j++)
ans = min(ans, dis(tp[i], tp[j]));

return ans;
}

int main()
{
int n, i, t;
cin >> t;
while(t--)
{
scanf("%d", &n);
for(i = 1; i <= n; i++)
{
p[i].flag = true;
scanf("%I64d%I64d", &p[i].x, &p[i].y);
}

for(i = n + 1; i <= 2 * n; i++)
{
p[i].flag = false;
scanf("%I64d%I64d", &p[i].x, &p[i].y);
}

n += n;
sort(p + 1, p + n + 1, cmp_x);
printf("%.3lf\n", solve(1, n, n));
}
return 0;
}