Add doctests for graphs_floyd_warshall.py

graphs/graphs_floyd_warshall.py

@@ -1,62 +1,112 @@
 # floyd_warshall.py
 """
-The problem is to find the shortest distance between all pairs of vertices in a
-weighted directed graph that can have negative edge weights.
+The problem is to find and return the shortest distance between all pairs of vertices
+in a weighted directed graph that can have negative edge weights.
 """
 
 
-def _print_dist(dist, v):
-    print("\nThe shortest path matrix using Floyd Warshall algorithm\n")
-    for i in range(v):
-        for j in range(v):
-            if dist[i][j] != float("inf"):
-                print(int(dist[i][j]), end="\t")
-            else:
-                print("INF", end="\t")
-        print()
+def floyd_warshall(graph: list[list[float]], vertex: int) -> tuple:
+    # 1. For all edges from v to n, distance[i][j] = weight(edge(i, j)).
+
+    # 2. distance[i][j] = min(distance[i][j], distance[i][k] + distance[k][j]).
 
+    # 3. Step 2 is true for each pair of vertices.Repeat for k vertex in the graph.
+
+    # 4. Whenever distance[i][j] is given a new minimum value,
+    #   next vertex[i][j] = next vertex[i][k].
 
-def floyd_warshall(graph, v):
     """
     :param graph: 2D array calculated from weight[edge[i, j]]
-    :type graph: List[List[float]]
+
     :param v: number of vertices
-    :type v: int
+
     :return: shortest distance between all vertex pairs
+
     distance[u][v] will contain the shortest distance from vertex u to v.
 
-    1. For all edges from v to n, distance[i][j] = weight(edge(i, j)).
-    3. The algorithm then performs distance[i][j] = min(distance[i][j], distance[i][k] +
-        distance[k][j]) for each possible pair i, j of vertices.
-    4. The above is repeated for each vertex k in the graph.
-    5. Whenever distance[i][j] is given a new minimum value, next vertex[i][j] is
-        updated to the next vertex[i][k].
+    # doctests:
+
+    >>> graph = [[0, 3, float('inf')], [2, 0, float('inf')],[float('inf'), 7, 0]]
+    >>> floyd_warshall(graph, 3)[0]
+    [[0, 3, inf], [2, 0, inf], [9, 7, 0]]
+
+    >>> graph = [[0, 1, 4],[float('inf'), 0, 2],[float('inf'), float('inf'), 0]]
+    >>> floyd_warshall(graph, 3)[0]
+    [[0, 1, 3], [inf, 0, 2], [inf, inf, 0]]
+
+    >>> graph = [[0, 0, 0],[0, 0, 0],[0, 0, 0]]
+    >>> floyd_warshall(graph, 3)[0]
+    [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
+
+    #Graph with all edge weights = infinity
+
+    >>> graph = [[float('inf'), float('inf'), float('inf')],
+    ... [float('inf'), float('inf'), float('inf')],
+    ... [float('inf'), float('inf'), float('inf')]]
+    >>> floyd_warshall(graph, 3)[0]
+    [[inf, inf, inf], [inf, inf, inf], [inf, inf, inf]]
+
+
+    #Handling negetive weighted graph:
+
+    >>> graph = [[0, -2, float('inf')],[float('inf'), 0, 3],[4, float('inf'), 0]]
+    >>> floyd_warshall(graph, 3)[0]
+    [[0, -2, 1], [7, 0, 3], [4, 2, 0]]
+
+
+    #Handling negetive weighted cycle:
+
+    >>> graph = [[0, -1, float('inf')],[float('inf'), 0, -2],[-3, float('inf'), 0]]
+    >>> floyd_warshall(graph, 3)[0]
+    [[-6, -7, -9], [-5, -6, -8], [-9, -10, -12]]
+
+
+    #Number of vertex in function argument should match number of vertex in graph:
+
+    >>> graph = [[0, -1, float('inf')],[float('inf'), 0, -2]]
+    >>> floyd_warshall(graph, 3)[0]
+    Traceback (most recent call last):
+        ...
+    IndexError: list index out of range
+
+
+    #Graph data type should be a 2D list:
+
+    >>> graph = "strings not allowed"
+    >>> floyd_warshall(graph, 3)[0]
+    Traceback (most recent call last):
+        ...
+    IndexError: string index out of range
     """
 
-    dist = [[float("inf") for _ in range(v)] for _ in range(v)]
+    dist = [[float("inf") for _ in range(vertex)] for _ in range(vertex)]
 
-    for i in range(v):
-        for j in range(v):
+    for i in range(vertex):
+        for j in range(vertex):
             dist[i][j] = graph[i][j]
-
             # check vertex k against all other vertices (i, j)
-    for k in range(v):
+
+    for k in range(vertex):
         # looping through rows of graph array
-        for i in range(v):
+
+        for i in range(vertex):
             # looping through columns of graph array
-            for j in range(v):
+
+            for j in range(vertex):
                 if (
                     dist[i][k] != float("inf")
                     and dist[k][j] != float("inf")
                     and dist[i][k] + dist[k][j] < dist[i][j]
                 ):
                     dist[i][j] = dist[i][k] + dist[k][j]
-
-    _print_dist(dist, v)
-    return dist, v
+    return dist, vertex
 
 
 if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+
     v = int(input("Enter number of vertices: "))
     e = int(input("Enter number of edges: "))