Network Delay Time (Dijkstra)

**Problem Statement:** Given the required input arguments, write an efficient algorithm to solve the **Network Delay Time (Dijkstra)** problem. Implement the required logic as specified by standard definitions for this classic algorithmic challenge. **Hint / Expected Approach:** Dijkstra's algorithm with min-heap **Edge Cases to Consider:** - (1) Source unreachable to some node - (2) Single node - (3) Negative weight (Dijkstra fails)

Examples

Example 1

Input: [[2,1,1],[2,3,1],[3,4,1]], 4, 2

Output: 2

Explanation: Classic

Example 2

Input: [[1,2,1]], 2, 1

Output: 1

Explanation: Single edge

Example 3

Input: [[1,2,1]], 2, 2

Output: -1

Explanation: Source can't reach node 1

Constraints

▪2 <= vertices <= 1000
▪0 <= edges <= 5000
▪Avoid infinite cycles during depth traversal

Watch Out For Edge Cases

▪Source unreachable to some node
▪Single node
▪Negative weight (Dijkstra fails)

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