POJ 1258 Agri-Net (MST-Kruscal)
链接:http://poj.org/problem?id=1258
Description
Farmer John ordered a high speed connection for his farm and is going to share his connectivity with the other farmers. To minimize cost, he wants to lay the minimum amount of optical fiber to connect his farm to all the other farms.
Given a list of how much fiber it takes to connect each pair of farms, you must find the minimum amount of fiber needed to connect them all together. Each farm must connect to some other farm such that a packet can flow from any one farm to any other farm.
The distance between any two farms will not exceed 100,000.
Input
Output
Sample Input
4 0 4 9 21 4 0 8 17 9 8 0 16 21 17 16 0
Sample Output
28
解题思路: 最简单的最小生成树的题目;MST-Kruscal
代码如下:
#include <iostream> #include <cstdio> #include <cstring> #include <cstdlib> #include <cmath> #include <vector> #include <string> #include <iomanip> #include <cassert> #include <algorithm> #define LC(x) (x<<1) #define RC(x) (LC(x)+1) #define PI (acos(-1)) #define EPS 1e-8 #define MAXN 111111 #define MAXM 222222 #define LL long long #define ULL unsigned long long #define INF 0x7fffffff #define pb push_back #define mp make_pair #define lowbit(x) (x&(-x)) #define RST(N)memset(N, 0, sizeof(N)) using namespace std; struct edge { int v, u, cost; }e[111*111]; bool cmp_e(const edge &a, const edge &b) { return a.cost < b.cost; } int ecnt, fa[111], n, v; void addedge(int u, int v, int cost) { e[++ ecnt].v = v, e[ecnt].u = u, e[ecnt].cost = cost; } int getf(int x) { return fa[x] == x ? x : fa[x] = getf(fa[x]); } int kruscal() { int sum = 0; for(int i = 1; i <= n; i ++) fa[i] = i; sort(e + 1, e + 1 + ecnt, cmp_e); for(int i = 1; i <= ecnt; i ++) { int u = e[i].u, v = e[i].v; u = getf(u), v = getf(v); if(u == v) continue; sum += e[i].cost; fa[u] = v; } return sum; } int main() { while(scanf("%d", &n) == 1) { ecnt = 0; for(int i = 1; i <= n; i ++) { for(int j = 1; j <= n; j ++) { scanf("%d", &v); if(v != 0) addedge(i, j, v); } } printf("%d\n", kruscal()); } return 0; }
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