POJ 1251 Jungle Roads (最小生成树 Kruskal克鲁斯卡尔算法)

#include <stdio.h>

#define MAX_ROADS 76
#define MAX_VILLAGES 27

struct ROAD{
int start;
int end;
int cost;
};

ROAD roadArray[MAX_ROADS];
int numOfRoads;
int roadNum;

int numOfVillages;

int parent[MAX_VILLAGES];

void roadCopy(ROAD *to, ROAD *from){
ROAD temproad;
temproad.start = from->start;
temproad.end = from->end;
temproad.cost = from->cost;
from->start = to->start;
from->end = to->end;
from->cost = to->cost;
to->start = temproad.start;
to->end = temproad.end;
to->cost = temproad.cost;
}
void quickSortroadsAccordingToCost(int start, int end){
if (start >= end){
return;
}
while (start < end){
int left = start;
int right = end;
ROAD pivotroad;
roadCopy(&pivotroad, &roadArray[start]);
while (left < right){
while (left < right && roadArray[right].cost >= pivotroad.cost){
right--;
}
roadCopy(&roadArray[left], &roadArray[right]);
while (left < right && roadArray[left].cost <= pivotroad.cost){
left++;
}
roadCopy(&roadArray[right], &roadArray[left]);
}
roadCopy(&roadArray[left], &pivotroad);
int pivot = left;
quickSortroadsAccordingToCost(start, pivot - 1);
start = pivot + 1;
}
}

int getParent(int villageNum){
while (parent[villageNum]){
villageNum = parent[villageNum];
}
return villageNum;
}
int main(){
//freopen("input.txt", "r", stdin);

while (1){
scanf("%d", &numOfVillages);
if (numOfVillages == 0){
return 0;
}

numOfRoads = 0;
int indexOfVillage;
for (indexOfVillage = 1; indexOfVillage <= numOfVillages; indexOfVillage++){
parent[indexOfVillage] = 0;
}

for (indexOfVillage = 1; indexOfVillage < numOfVillages; indexOfVillage++){
char villageLetter;
int numOfAdjaRoads;
scanf(" %c %d", &villageLetter, &numOfAdjaRoads);
int start = villageLetter - 'A' + 1;
int indexOfRoad;
for (indexOfRoad = 1; indexOfRoad <= numOfAdjaRoads; indexOfRoad++){
int cost;
scanf(" %c %d", &villageLetter, &cost);
int end = villageLetter - 'A' + 1;
numOfRoads++;
roadNum = numOfRoads;
roadArray[roadNum].start = start;
roadArray[roadNum].end = end;
roadArray[roadNum].cost = cost;
}
}

quickSortroadsAccordingToCost(1, numOfRoads);

int minTotalCost = 0;
int indexOfRoad;
for (indexOfRoad = 1; indexOfRoad <= numOfRoads; indexOfRoad++){
int start = roadArray[indexOfRoad].start;
int end = roadArray[indexOfRoad].end;
int parentOfStart = getParent(start);
int parentOfEnd = getParent(end);
if ( parentOfStart != parentOfEnd ){
parent[parentOfStart] = parentOfEnd;
minTotalCost += roadArray[indexOfRoad].cost;
}
}

printf("%d\n", minTotalCost);
}
}