UVA 1151 买还是建(最小生成树)
买还是建
紫书P358
【题目链接】买还是建
【题目类型】最小生成树
&题解:
这题真的心累,看了3天,最后照着码还是wa,先放lrj代码,以后再看吧
&代码:
// UVa1151 Buy or Build
// Rujia Liu
#include <cstdio>
#include <cmath>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
const int maxn = 1000 + 10;
const int maxq = 8;
int n;
int x[maxn], y[maxn], cost[maxq];
vector<int> subn[maxq];
int pa[maxn];
int findset(int x) { return pa[x] != x ? pa[x] = findset(pa[x]) : x; }
struct Edge {
int u, v, d;
Edge(int u, int v, int d):u(u),v(v),d(d) {}
bool operator < (const Edge& rhs) const {
return d < rhs.d;
}
};
// initialize pa and sort e before calling this method
// cnt is the current number of components
int MST(int cnt, const vector<Edge>& e, vector<Edge>& used) {
if(cnt == 1) return 0;
int m = e.size();
int ans = 0;
used.clear();
for(int i = 0; i < m; i++) {
int u = findset(e[i].u), v = findset(e[i].v);
int d = e[i].d;
if(u != v) {
pa[u] = v;
ans += d;
used.push_back(e[i]);
if(--cnt == 1) break;
}
}
return ans;
}
int main() {
int T, q;
scanf("%d", &T);
while(T--) {
scanf("%d%d", &n, &q);
for(int i = 0; i < q; i++) {
int cnt;
scanf("%d%d", &cnt, &cost[i]);
subn[i].clear();
while(cnt--) {
int u;
scanf("%d", &u);
subn[i].push_back(u-1);
}
}
for(int i = 0; i < n; i++) scanf("%d%d", &x[i], &y[i]);
vector<Edge> e, need;
for(int i = 0; i < n; i++)
for(int j = i+1; j < n; j++) {
int c = (x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]);
e.push_back(Edge(i, j, c));
}
for(int i = 0; i < n; i++) pa[i] = i;
sort(e.begin(), e.end());
int ans = MST(n, e, need);
for(int mask = 0; mask < (1<<q); mask++) {
// union cities in the same sub-network
for(int i = 0; i < n; i++) pa[i] = i;
int cnt = n, c = 0;
for(int i = 0; i < q; i++) if(mask & (1<<i)) {
c += cost[i];
for(int j = 1; j < subn[i].size(); j++) {
int u = findset(subn[i][j]), v = findset(subn[i][0]);
if(u != v) { pa[u] = v; cnt--; }
}
}
vector<Edge> dummy;
ans = min(ans, c + MST(cnt, need, dummy));
}
printf("%d\n", ans);
if(T) printf("\n");
}
return 0;
}