{ "data": { "question": { "questionId": "1912", "questionFrontendId": "1786", "boundTopicId": null, "title": "Number of Restricted Paths From First to Last Node", "titleSlug": "number-of-restricted-paths-from-first-to-last-node", "content": "
There is an undirected weighted connected graph. You are given a positive integer n
which denotes that the graph has n
nodes labeled from 1
to n
, and an array edges
where each edges[i] = [ui, vi, weighti]
denotes that there is an edge between nodes ui
and vi
with weight equal to weighti
.
A path from node start
to node end
is a sequence of nodes [z0, z1, z2, ..., zk]
such that z0 = start
and zk = end
and there is an edge between zi
and zi+1
where 0 <= i <= k-1
.
The distance of a path is the sum of the weights on the edges of the path. Let distanceToLastNode(x)
denote the shortest distance of a path between node n
and node x
. A restricted path is a path that also satisfies that distanceToLastNode(zi) > distanceToLastNode(zi+1)
where 0 <= i <= k-1
.
Return the number of restricted paths from node 1
to node n
. Since that number may be too large, return it modulo 109 + 7
.
\n
Example 1:
\n\n\nInput: n = 5, edges = [[1,2,3],[1,3,3],[2,3,1],[1,4,2],[5,2,2],[3,5,1],[5,4,10]]\nOutput: 3\nExplanation: Each circle contains the node number in black and its distanceToLastNode value in blue.
The three restricted paths are:\n1) 1 --> 2 --> 5\n2) 1 --> 2 --> 3 --> 5\n3) 1 --> 3 --> 5\n
\n\nExample 2:
\n\n\nInput: n = 7, edges = [[1,3,1],[4,1,2],[7,3,4],[2,5,3],[5,6,1],[6,7,2],[7,5,3],[2,6,4]]\nOutput: 1\nExplanation: Each circle contains the node number in black and its distanceToLastNode value in blue.
The only restricted path is 1 --> 3 --> 7.\n
\n\n\n
Constraints:
\n\n1 <= n <= 2 * 104
n - 1 <= edges.length <= 4 * 104
edges[i].length == 3
1 <= ui, vi <= n
ui != vi
1 <= weighti <= 105
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