AtCoder Beginner Contest 051
D
Candidates of No Shortest Paths
AtCoder
⌀ 1566
原题
← C→
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Problem Statement

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You are given an undirected connected weighted graph with $N$ vertices and $M$ edges that contains neither self-loops nor double edges. The $i$-th $(1≤i≤M)$ edge connects vertex $a_i$ and vertex $b_i$ with a distance of $c_i$. Here, a self-loop is an edge where $a_i = b_i (1≤i≤M)$, and double edges are two edges where $(a_i,b_i)=(a_j,b_j)$ or $(a_i,b_i)=(b_j,a_j) (1≤i<j≤M)$. A connected graph is a graph where there is a path between every pair of different vertices. Find the number of the edges that are not contained in any shortest path between any pair of different vertices.

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Constraints

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  • $2≤N≤100$
  • $N-1≤M≤min(N(N-1)/2,1000)$
  • $1≤a_i,b_i≤N$
  • $1≤c_i≤1000$
  • $c_i$ is an integer.
  • The given graph contains neither self-loops nor double edges.
  • The given graph is connected.
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Input

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The input is given from Standard Input in the following format:

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N M
a_1 b_1 c_1
a_2 b_2 c_2
:
a_M b_M c_M

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Output

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Print the number of the edges in the graph that are not contained in any shortest path between any pair of different vertices.

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样例

Input #1
3 3
1 2 1
1 3 1
2 3 3
Output #1
1
In the given graph, the shortest paths between all pairs of different vertices are as follows: - The shortest path from vertex $1$ to vertex $2$ is: vertex $1$ → vertex $2$, with the length of $1$. - The shortest path from vertex $1$ to vertex $3$ is: vertex $1$ → vertex $3$, with the length of $1$. - The shortest path from vertex $2$ to vertex $1$ is: vertex $2$ → vertex $1$, with the length of $1$. - The shortest path from vertex $2$ to vertex $3$ is: vertex $2$ → vertex $1$ → vertex $3$, with the length of $2$. - The shortest path from vertex $3$ to vertex $1$ is: vertex $3$ → vertex $1$, with the length of $1$. - The shortest path from vertex $3$ to vertex $2$ is: vertex $3$ → vertex $1$ → vertex $2$, with the length of $2$. Thus, the only edge that is not contained in any shortest path, is the edge of length $3$ connecting vertex $2$ and vertex $3$, hence the output should be $1$.
Input #2
3 2
1 2 1
2 3 1
Output #2
0
Every edge is contained in some shortest path between some pair of different vertices.
题目信息
题号
abc051_d
时间限制
2 s
内存限制
256 MB

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