743. Network Delay Time

Medium
You are given a network of n nodes, labeled from 1 to n. You are also given times, a list of travel times as directed edges times[i] = (ui, vi, wi), where ui is the source node, vi is the target node, and wi is the time it takes for a signal to travel from source to target.
We will send a signal from a given node k. Return the minimum time it takes for all the n nodes to receive the signal. If it is impossible for all the n nodes to receive the signal, return -1.
Example 1:
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​
Input: times = [[2,1,1],[2,3,1],[3,4,1]], n = 4, k = 2
Output: 2
Example 2:
Input: times = [[1,2,1]], n = 2, k = 1
Output: 1
Example 3:
Input: times = [[1,2,1]], n = 2, k = 2
Output: -1
Constraints:
  • 1 <= k <= n <= 100
  • 1 <= times.length <= 6000
  • times[i].length == 3
  • 1 <= ui, vi <= n
  • ui != vi
  • 0 <= wi <= 100
  • All the pairs (ui, vi) are unique. (i.e., no multiple edges.)

解題

func networkDelayTime(times [][]int, n int, k int) int {
// 從 source 出發,求到全部節點的最短路徑
// 有節點不能到達,回傳 -1
dist := make([]int, n)
​
for i := 0 ; i < n ; i++ {
dist[i] = math.MaxInt32
}
dist[k - 1] = 0 //source
​
for i := 1; i < n ; i++ {
for _, time := range times {
dist[time[1] - 1] = min(dist[time[1] - 1], dist[time[0] - 1] + time[2])
}
}
​
ans := -1
for _, dis := range dist {
if dis == math.MaxInt32 { //有節點不能到達
return -1
}
​
if dis > ans {
ans = dis
}
}
​
return ans
}
​
func min(a, b int) int {
if a < b { return a }
return b
}