P25791 [AtCoder] Road Reduction
普及+
题目描述

Problem Statement

The Kingdom of AtCoder has $N cities called City 1,2,\ldots,N$ and $M roads called Road 1,2,\ldots,M$.
Road i connects Cities A_i and B_i bidirectionally and has a length of C_i.
One can travel between any two cities using some roads.
Under financial difficulties, the kingdom has decided to maintain only N-1 roads so that one can still travel between any two cities using those roads and abandon the rest.
Let d_i be the total length of the roads one must use when going from City 1 to City i using only maintained roads. Print a choice of roads to maintain that minimizes $d_2+d_3+\ldots+d_N$.

Input

Input is given from Standard Input in the following format:
N M
A_1 B_1 C_1
A_2 B_2 C_2
$\vdots$
A_M B_M C_M

Output

Print the indices of roads to maintain, in arbitrary order, with spaces in between.
If multiple solutions exist, you may print any of them.

Constraints

  • $2 \leq N \leq 2\times 10^5$
  • $N-1 \leq M \leq 2\times 10^5$
  • $1 \leq A_i < B_i \leq N$
  • $(A_i,B_i)\neq(A_j,B_j)$ if $i\neq j$.
  • $1\leq C_i \leq 10^9$
  • One can travel between any two cities using some roads.
  • All values in input are integers.

Sample Input 1

3 3
1 2 1
2 3 2
1 3 10

Sample Output 1

1 2

Here are the possible choices of roads to maintain and the corresponding values of d_i.

  • Maintain Road 1 and 2: d_2=1, d_3=3.
  • Maintain Road 1 and 3: d_2=1, d_3=10.
  • Maintain Road 2 and 3: d_2=12, d_3=10.

Thus, maintaining Road 1 and 2 minimizes d_2+d_3.

Sample Input 2

4 6
1 2 1
1 3 1
1 4 1
2 3 1
2 4 1
3 4 1

Sample Output 2

3 1 2

输入格式

见题面 Input 部分

输出格式

见题面 Output 部分

样例输入
3 3 1 2 1 2 3 2 1 3 10
样例输出
1 2