func_code_string: #include <bits/stdc++.h>   using namespace std;   struct debugger {     template <typename T>     debugger& operator,(const T& v) {       cerr << v <<   t ;       return *this;     }   } dbg;   template <class T>   void setmax(T& a, T b) {     if (a < b) a = b;   }   template <class T>   void setmin(T& a, T b) {     if (b < a) a = b;   }   template <class T>   T Abs(T x) {     return x > 0 ? x : -x;   }   template <class T>   inline T sqr(T x) {     return x * x;   }   template <class T>   inline T Mod(T n, T m) {     return (n % m + m) % m;   }   template <class T>   string toString(T n) {     ostringstream oss;     oss << n;     oss.flush();     return oss.str();   }   int toInt(string s) {     int r = 0;     istringstream sin(s);     sin >> r;     return r;   }   bool isVowel(char ch) {     ch = tolower(ch);     if (ch ==  a  || ch ==  e  || ch ==  i  || ch ==  o  || ch ==  u )       return true;     return false;   }   bool isUpper(char c) { return c >=  A  && c <=  Z ; }   bool isLower(char c) { return c >=  a  && c <=  z ; }   long long Pow(long long B, long long P) {     long long R = 1;     while (P > 0) {       if (P % 2 == 1) R = (R * B);       P /= 2;       B = (B * B);     }     return R;   }   int BigMod(long long B, long long P, long long M) {     long long R = 1;     while (P > 0) {       if (P % 2 == 1) {         R = (R * B) % M;       }       P /= 2;       B = (B * B) % M;     }     return (int)R;   }   void binprint(long long mask, long long n) {     long long i;     string s =   ;     do {       s += (mask % 2 +  0 );       mask /= 2;     } while (mask);     reverse(s.begin(), s.end());     s = string(max(n - (int)s.size(), 0LL),  0 ) + s;     for (i = (int)s.size() - n; i < (int)s.size(); i++) printf( %c , s[i]);     printf(  n );   }   void ASCII_Chart() {     int i, j, k;     printf( ASCII Chart:(30-129) n );     for (i = 30; i < 50; i++) {       for (j = 0; j < 5; j++) {         k = i + j * 20;         printf( %3d--->  %c     , k, k);       }       printf(  n );     }   }   struct edges {     int u, v, ind;     double w;     edges(int _u = 0, int _v = 0, double _w = 0, int _ind = 0) {       u = _u;       v = _v;       w = _w;       ind = _ind;     }   };   vector<edges> e, e1, e2;   int N, M, p[5050], cnt, K;   bool comp(edges p, edges q) { return p.w < q.w; }   void precalc() {     e1.clear();     e2.clear();     for (int i = 0; i < M; i++) {       if (e[i].u == 0 || e[i].v == 0)         e1.push_back(e[i]);       else         e2.push_back(e[i]);     }     sort(e1.begin(), e1.end(), comp);     sort(e2.begin(), e2.end(), comp);   }   void merge(vector<edges> e3) {     e.clear();     int i = 0, j = 0;     while (i < e2.size() && j < e3.size()) {       if (e2[i].w < e3[j].w)         e.push_back(e2[i++]);       else         e.push_back(e3[j++]);     }     for (; i < e2.size(); i++) e.push_back(e2[i]);     for (; j < e3.size(); j++) e.push_back(e3[j]);     return;   }   int find_parent(int u) {     if (u != p[u]) p[u] = find_parent(p[u]);     return p[u];   }   void Union(int a, int b) { p[b] = a; }   int calc_k(double x) {     int ret, i;     vector<edges> e3;     for (i = 0; i < e1.size(); i++) {       e3.push_back(e1[i]);       e3[i].w += x;     }     merge(e3);     for (i = 0; i < N; i++) p[i] = i;     cnt = ret = 0;     for (i = 0; i < M; i++) {       int a = find_parent(e[i].u);       int b = find_parent(e[i].v);       if (a != b) {         e[i].ind = -e[i].ind;         Union(a, b);         if (e[i].u == 0 || e[i].v == 0) ret++;         cnt++;       }     }     return ret;   }   bool solve() {     double low = -10001000, high = 10001000;     for (int i = 0; i < e1.size(); i++) e1[i].w += (i * 1e-7);     while (fabs(low - high) > 1e-7) {       double mid = (low + high) / 2;       if (calc_k(mid) > K)         low = mid;       else         high = mid;     }     if (calc_k(low) == K) return true;     return (calc_k(high) == K);   }   int main() {     int i, j, test, Case = 1, u, v, w;     test = 1;     while (test--) {       scanf( %d %d %d , &N, &M, &K);       e.clear();       for (i = 0; i < M; i++) {         scanf( %d %d %d , &u, &v, &w);         e.push_back(edges(u - 1, v - 1, w, i + 1));       }       if (K == 0) {         if (N <= 1)           printf( 0 n );         else           printf( -1 n );         continue;       }       precalc();       calc_k(0);       if (cnt != N - 1 || e1.size() < K) {         printf( -1.. n );         continue;       }       double total = 0;       int ind;       if (solve()) {         printf( %d n , N - 1);         for (i = 0; i < M; i++)           if (e[i].ind <= 0) {             printf( %d  , -e[i].ind);           }         printf(  n );       } else         printf( -1__- n );     }     return 0;   }   