UVa 10034 Freckles 解答

/*
* 10034.cc
*
*  Created on: Jan 8, 2013
*      Author: root
*/
#include <stdio.h>
#include <math.h>
#include <algorithm>

typedef struct Edge_ {
int start;
int stop;
double weight;
}Edge;

typedef struct Node_ {
double x;
double y;
}Node;

Node node_list[100];
Edge edge_list[5000];
int edge_number;
int father[100];

bool Compare(Edge a, Edge b) {
return a.weight < b.weight;
}

double ComputeEdge(int start, int stop) {
double x = node_list[start].x-node_list[stop].x;
double y = node_list[start].y-node_list[stop].y;
return sqrt(x*x + y*y);
}

//并查集的查询及优化
int FindFather(int point) {
return father[point] == point ? point : father[point] = FindFather(father[point]);
}

double Compute(int points) {
double sum = 0.0;
edge_number = 0;
for (int i=0; i<points; i++)
for (int j=i+1; j<points; j++) {
edge_list[edge_number].start = i;
edge_list[edge_number].stop = j;
edge_list[edge_number].weight = ComputeEdge(i, j);
edge_number++;
}

for (int i=0; i<points; i++)
father[i] = i;
std::sort(edge_list, edge_list + edge_number, Compare);

for (int i=0; i<edge_number; i++) {
int pa1 = FindFather(edge_list[i].start);
int pa2 = FindFather(edge_list[i].stop);
if (pa1 != pa2) {
sum += edge_list[i].weight;
father[pa1] = pa2;//并查集的合并
}
}
return sum;
}

int main(int argc, char** argv) {
int cases;
scanf("%d", &cases);
for (int i=0; i<cases; i++) {
int points;
scanf("%d", &points);
for (int j=0; j<points; j++) {
scanf("%lf%lf", &node_list[j].x, &node_list[j].y);
}
if (i != 0)
printf("\n");
printf("%.2f\n", Compute(points));
}
return 0;
}