带权并查集。
1 /* 3047 */ 2 #include <iostream> 3 #include <string> 4 #include <map> 5 #include <queue> 6 #include <set> 7 #include <stack> 8 #include <vector> 9 #include <deque> 10 #include <algorithm> 11 #include <cstdio> 12 #include <cmath> 13 #include <ctime> 14 #include <cstring> 15 #include <climits> 16 #include <cctype> 17 #include <cassert> 18 #include <functional> 19 #include <iterator> 20 #include <iomanip> 21 using namespace std; 22 //#pragma comment(linker,"/STACK:102400000,1024000") 23 24 #define sti set<int> 25 #define stpii set<pair<int, int> > 26 #define mpii map<int,int> 27 #define vi vector<int> 28 #define pii pair<int,int> 29 #define vpii vector<pair<int,int> > 30 #define rep(i, a, n) for (int i=a;i<n;++i) 31 #define per(i, a, n) for (int i=n-1;i>=a;--i) 32 #define clr clear 33 #define pb push_back 34 #define mp make_pair 35 #define fir first 36 #define sec second 37 #define all(x) (x).begin(),(x).end() 38 #define SZ(x) ((int)(x).size()) 39 #define lson l, mid, rt<<1 40 #define rson mid+1, r, rt<<1|1 41 42 const int maxn = 5e4+5; 43 int fa[maxn], dis[maxn]; 44 45 int find(int x) { 46 if (fa[x] == x) 47 return x; 48 49 int tmp = fa[x]; 50 fa[x] = find(fa[x]); 51 dis[x] += dis[tmp]; 52 53 return fa[x]; 54 } 55 56 bool merge(int u, int v, int w) { 57 int fu = find(u); 58 int fv = find(v); 59 60 if (fu == fv) { 61 if (dis[u]+w!=dis[v]) 62 return false; 63 return true; 64 } 65 66 fa[fv] = fu; 67 dis[fv] = dis[u] + w - dis[v]; 68 69 return true; 70 } 71 72 int main() { 73 ios::sync_with_stdio(false); 74 #ifndef ONLINE_JUDGE 75 freopen("data.in", "r", stdin); 76 freopen("data.out", "w", stdout); 77 #endif 78 79 int n, m; 80 int u, v, w; 81 int ans; 82 83 while (scanf("%d %d", &n, &m) != EOF) { 84 rep(i, 1, n+1) { 85 fa[i] = i; 86 dis[i] = 0; 87 } 88 ans = 0; 89 while (m--) { 90 scanf("%d %d %d", &u, &v, &w); 91 if (!merge(u, v, w)) 92 ++ans; 93 } 94 printf("%d ", ans); 95 } 96 97 #ifndef ONLINE_JUDGE 98 printf("time = %d. ", (int)clock()); 99 #endif 100 101 return 0; 102 }