【并查集】 HDOJ 4424 Conquer a New Region

神奇的并查集。。。。参考：http://blog.csdn.net/shuangde800/article/details/8872353

#include <iostream>#include <queue> #include <stack> #include <map> #include <set> #include <bitset> #include <cstdio> #include <algorithm> #include <cstring> #include <climits>#include <cstdlib>#include <cmath>#include <time.h>#define maxn 200005#define maxm 200005#define eps 1e-7#define mod 1000000007#define INF 0x3f3f3f3f#define PI (acos(-1.0))#define lowbit(x) (x&(-x))#define mp make_pair#define ls o<<1#define rs o<<1 | 1#define lson o<<1, L, mid #define rson o<<1 | 1, mid+1, R#define pii pair<int, int>#pragma comment(linker, "/STACK:16777216")typedef long long LL;typedef unsigned long long ULL;//typedef int LL;using namespace std;LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}// headstruct node{int u, v, w;}e[maxm];int f[maxn];int c[maxn];LL res[maxn];int n;LL ans;int find(int x){return x == f[x] ? f[x] : find(f[x]);}void merge(int a, int b, int w){int aa = find(a), bb = find(b);if(aa != bb) {LL res1 = res[aa] + (LL)w * c[bb];LL res2 = res[bb] + (LL)w * c[aa];if(res1 > res2) {f[bb] = aa;c[aa] += c[bb];res[aa] = res1;}else {f[aa] = bb;c[bb] += c[aa];res[bb] = res2;}}}int cmp(node a, node b){return a.w > b.w;}void read(){for(int i = 0; i <= n; i++) c[i] = 1;for(int i = 0; i <= n; i++) f[i] = i;for(int i = 0; i <= n; i++) res[i] = 0;ans = 0;for(int i = 1; i < n; i++)scanf("%d%d%d", &e[i].u, &e[i].v, &e[i].w);}void work(){sort(e+1, e+n, cmp);for(int i = 1; i < n; i++) merge(e[i].u, e[i].v, e[i].w);printf("%I64d\n", res[find(1)]);}int main(){while(scanf("%d", &n)!=EOF) {read();work();}return 0;}