POJ 1861 Networks

并查集 + 贪心 + 快速排序 求最小生成树 

#include <iostream>#include <memory>#define MAX_HUB_NUM 1005#define MAX_EDGE_NUM 15005using namespace std;int edge[3][MAX_EDGE_NUM + 1];int head[MAX_HUB_NUM + 1];int resEdge[MAX_EDGE_NUM + 1];int hub_num;int edge_num;void swap1(int pos1, int pos2){int temp0 = edge[0][pos2];int temp1 = edge[1][pos2];int temp2 = edge[2][pos2];edge[0][pos2] = edge[0][pos1];edge[1][pos2] = edge[1][pos1];edge[2][pos2] = edge[2][pos1];edge[0][pos1] = temp0;edge[1][pos1] = temp1;edge[2][pos1] = temp2;}void swap2(int pos1, int pos2){int temp = resEdge[pos2];resEdge[pos2] = resEdge[pos1];resEdge[pos1] = temp;}int comp1(int pos1, int pos2){if(edge[0][pos1] < edge[0][pos2])return -1;else if(edge[0][pos1] == edge[0][pos2])return 0;elsereturn 1;}int comp2(int p1, int p2){int pos1 = resEdge[p1];int pos2 = resEdge[p2];if(edge[1][pos1] < edge[1][pos2])return -1;else if(edge[1][pos1] == edge[1][pos2]){if(edge[2][pos1]  < edge[2][pos2])return -1;else if(edge[2][pos1]  == edge[2][pos2])return 0;elsereturn 1;}elsereturn 1;}void fast_sort(int start, int end, int (*comp)(int pos1, int pos2), void (*swap)(int pos1, int pos2)){if(start < end){int pos_s = start;int pos_e = end + 1;while(true){while(++pos_s < end && comp(start, pos_s) == 1);while(--pos_e > start && comp(start, pos_e) == -1);if(pos_s < pos_e)swap(pos_s, pos_e);elsebreak;}swap(start, pos_e);fast_sort(start, pos_e - 1, comp, swap);fast_sort(pos_e + 1, end, comp, swap);}}void init_input(){memset(edge, 0, sizeof(edge));memset(head, 0, sizeof(head));memset(resEdge, 0, sizeof(resEdge));cin>>hub_num>>edge_num;for(int i = 1; i <= edge_num; i++){cin>>edge[1][i]>>edge[2][i]>>edge[0][i];if(i <= hub_num)head[i] = i;}fast_sort(1, edge_num, &comp1, &swap1);}int find(int x){if(head[x] == x)return x;elsereturn find(head[x]);}void join(int x, int y){int head1 = find(x);int head2 = find(y);head[head1] = head2;}int main(){int i = 1;int total = 0;int maxv = 0;int pos1, pos2, curVal;init_input();while(i <= edge_num && total < (hub_num - 1)){curVal = edge[0][i];pos1 = find(edge[1][i]);pos2 = find(edge[2][i]);if(pos1 != pos2){if(curVal > maxv)maxv = curVal;join(pos1, pos2);total ++;resEdge[total] = i;}i++;}cout<<maxv<<endl;cout<<total<<endl;fast_sort(1, total, &comp2, &swap2);for(i = 1; i <= total; i++){cout<<edge[1][resEdge[i]]<<" "<<edge[2][resEdge[i]]<<endl;}return 0;}