Add doctests to dijkstra_2.py

Author: pratyushbanerjee

graphs/dijkstra_2.py

@@ -9,6 +9,13 @@ def print_dist(dist, v):
 
 
 def min_dist(mdist, vset, v):
+    """
+    Returns the vertex with the minimum distance from the source vertex\
+        that has not been visited.
+
+    >>> min_dist([0, 1, 6], [True, False, False], 3)
+    1
+    """
     min_val = float("inf")
     min_ind = -1
     for i in range(v):
@@ -19,6 +26,20 @@ def min_dist(mdist, vset, v):
 
 
 def dijkstra(graph, v, src):
+    """
+    Calculate the shortest path from source to all other vertices\
+        using Dijkstra's algorithm.
+
+    >>> graph = [[0.0, 1.0, 6.0],\
+                [float("inf"), 0.0, 3.0],\
+                [float("inf"), float("inf"), 0.0]]
+    >>> dijkstra(graph, 3, 0) # doctest: +NORMALIZE_WHITESPACE
+    <BLANKLINE>
+    Vertex Distance
+    0    0
+    1    1
+    2    4
+    """
     mdist = [float("inf") for _ in range(v)]
     vset = [False for _ in range(v)]
     mdist[src] = 0.0