Adding Doctests to floyd_warshall.py (#11690)

* Ruff test resolution

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

dynamic_programming/floyd_warshall.py

@@ -12,19 +12,58 @@ def __init__(self, n=0):  # a graph with Node 0,1,...,N-1
         ]  # dp[i][j] stores minimum distance from i to j
 
     def add_edge(self, u, v, w):
+        """
+        Adds a directed edge from node u
+        to node v with weight w.
+
+        >>> g = Graph(3)
+        >>> g.add_edge(0, 1, 5)
+        >>> g.dp[0][1]
+        5
+        """
         self.dp[u][v] = w
 
     def floyd_warshall(self):
+        """
+        Computes the shortest paths between all pairs of
+        nodes using the Floyd-Warshall algorithm.
+
+        >>> g = Graph(3)
+        >>> g.add_edge(0, 1, 1)
+        >>> g.add_edge(1, 2, 2)
+        >>> g.floyd_warshall()
+        >>> g.show_min(0, 2)
+        3
+        >>> g.show_min(2, 0)
+        inf
+        """
         for k in range(self.n):
             for i in range(self.n):
                 for j in range(self.n):
                     self.dp[i][j] = min(self.dp[i][j], self.dp[i][k] + self.dp[k][j])
 
     def show_min(self, u, v):
+        """
+        Returns the minimum distance from node u to node v.
+
+        >>> g = Graph(3)
+        >>> g.add_edge(0, 1, 3)
+        >>> g.add_edge(1, 2, 4)
+        >>> g.floyd_warshall()
+        >>> g.show_min(0, 2)
+        7
+        >>> g.show_min(1, 0)
+        inf
+        """
         return self.dp[u][v]
 
 
 if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+
+    # Example usage
     graph = Graph(5)
     graph.add_edge(0, 2, 9)
     graph.add_edge(0, 4, 10)
@@ -38,5 +77,9 @@ def show_min(self, u, v):
     graph.add_edge(4, 2, 4)
     graph.add_edge(4, 3, 9)
     graph.floyd_warshall()
-    graph.show_min(1, 4)
-    graph.show_min(0, 3)
+    print(
+        graph.show_min(1, 4)
+    )  # Should output the minimum distance from node 1 to node 4
+    print(
+        graph.show_min(0, 3)
+    )  # Should output the minimum distance from node 0 to node 3