Add doctests and type hints to graphs/dijkstra_2.py to improve coverage

Author: anshikasaini914

graphs/dijkstra_2.py

@@ -1,58 +1,93 @@
-def print_dist(dist, v):
-    print("\nVertex Distance")
-    for i in range(v):
-        if dist[i] != float("inf"):
-            print(i, "\t", int(dist[i]), end="\t")
-        else:
-            print(i, "\t", "INF", end="\t")
-        print()
+"""
+Dijkstra's Algorithm Implementation.
 
+This module provides an implementation of Dijkstra's algorithm to find the
+shortest paths from a source vertex to all other vertices in a weighted directed graph.
+
+The graph is represented using an adjacency matrix where `float("inf")` represents
+no direct edge between two vertices.
+
+Example:
+    >>> graph = [
+    ...     [0, 4, float("inf"), float("inf"), float("inf"), float("inf"), float("inf"), 8, float("inf")],
+    ...     [4, 0, 8, float("inf"), float("inf"), float("inf"), float("inf"), 11, float("inf")],
+    ...     [float("inf"), 8, 0, 7, float("inf"), 4, float("inf"), float("inf"), 2],
+    ...     [float("inf"), float("inf"), 7, 0, 9, 14, float("inf"), float("inf"), float("inf")],
+    ...     [float("inf"), float("inf"), float("inf"), 9, 0, 10, float("inf"), float("inf"), float("inf")],
+    ...     [float("inf"), float("inf"), 4, 14, 10, 0, 2, float("inf"), float("inf")],
+    ...     [float("inf"), float("inf"), float("inf"), float("inf"), float("inf"), 2, 0, 1, 6],
+    ...     [8, 11, float("inf"), float("inf"), float("inf"), float("inf"), 1, 0, 7],
+    ...     [float("inf"), float("inf"), 2, float("inf"), float("inf"), float("inf"), 6, 7, 0],
+    ... ]
+    >>> dijkstra(graph, 0)
+    [0, 4, 12, 19, 21, 11, 9, 8, 14]
+"""
+
+from typing import List
 
-def min_dist(mdist, vset, v):
-    min_val = float("inf")
-    min_ind = -1
-    for i in range(v):
-        if (not vset[i]) and mdist[i] < min_val:
-            min_ind = i
-            min_val = mdist[i]
-    return min_ind
 
+def _min_dist(dist: List[float], visited: List[bool]) -> int:
+    """
+    Find the vertex with the minimum distance value from the set of
+    vertices that have not yet been visited.
+
+    Args:
+        dist: List of current shortest distances from the source.
+        visited: Boolean list indicating visited vertices.
+
+    Returns:
+        Index of the vertex with the minimum distance value.
+    """
+    min_val = float("inf")
+    min_index = -1
+    for i, d in enumerate(dist):
+        if not visited[i] and d < min_val:
+            min_val = d
+            min_index = i
+    return min_index
 
-def dijkstra(graph, v, src):
-    mdist = [float("inf") for _ in range(v)]
-    vset = [False for _ in range(v)]
-    mdist[src] = 0.0
 
-    for _ in range(v - 1):
-        u = min_dist(mdist, vset, v)
-        vset[u] = True
+def dijkstra(graph: List[List[float]], src: int) -> List[float]:
+    """
+    Compute shortest paths from a source vertex to all other vertices
+    using Dijkstra's algorithm.
 
-        for i in range(v):
-            if (
-                (not vset[i])
-                and graph[u][i] != float("inf")
-                and mdist[u] + graph[u][i] < mdist[i]
-            ):
-                mdist[i] = mdist[u] + graph[u][i]
+    Args:
+        graph: Adjacency matrix representing the weighted graph.
+        src: Source vertex index.
 
-    print_dist(mdist, i)
+    Returns:
+        A list containing the shortest distance from the source to each vertex.
 
+    Raises:
+        ValueError: If the source vertex index is invalid.
 
-if __name__ == "__main__":
-    V = int(input("Enter number of vertices: ").strip())
-    E = int(input("Enter number of edges: ").strip())
+    Example:
+        >>> graph = [
+        ...     [0, 4, float("inf"), float("inf")],
+        ...     [4, 0, 8, float("inf")],
+        ...     [float("inf"), 8, 0, 7],
+        ...     [float("inf"), float("inf"), 7, 0],
+        ... ]
+        >>> dijkstra(graph, 0)
+        [0, 4, 12, 19]
+    """
+    num_vertices = len(graph)
+    if src < 0 or src >= num_vertices:
+        raise ValueError("Source vertex index out of range")
 
-    graph = [[float("inf") for i in range(V)] for j in range(V)]
+    dist = [float("inf")] * num_vertices
+    visited = [False] * num_vertices
+    dist[src] = 0.0
 
-    for i in range(V):
-        graph[i][i] = 0.0
+    for _ in range(num_vertices - 1):
+        u = _min_dist(dist, visited)
+        if u == -1:
+            break  # Remaining vertices are unreachable
+        visited[u] = True
 
-    for i in range(E):
-        print("\nEdge ", i + 1)
-        src = int(input("Enter source:").strip())
-        dst = int(input("Enter destination:").strip())
-        weight = float(input("Enter weight:").strip())
-        graph[src][dst] = weight
+        for v in range(num_vertices):
+            if not visited[v] and graph[u][v] != float("inf") and dist[u] + graph[u][v] < dist[v]:
+                dist[v] = dist[u] + graph[u][v]
 
-    gsrc = int(input("\nEnter shortest path source:").strip())
-    dijkstra(graph, V, gsrc)
+    return [int(d) if d != float("inf") else float("inf") for d in dist]