From 0ceeb27fb663ac2e5274a8784c8d453d947afe97 Mon Sep 17 00:00:00 2001
From: Muhammad Junaid <junaid1460@gmail.com>
Date: Sun, 1 Oct 2017 09:33:41 +0530
Subject: [PATCH] floyd warshall algorithm with path generator

---
 .../floyd-warshall-with-path-generator.py     | 67 +++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 utilities/python/floyd-warshall-with-path-generator.py

diff --git a/utilities/python/floyd-warshall-with-path-generator.py b/utilities/python/floyd-warshall-with-path-generator.py
new file mode 100644
index 00000000..2979422f
--- /dev/null
+++ b/utilities/python/floyd-warshall-with-path-generator.py
@@ -0,0 +1,67 @@
+from collections import defaultdict
+import math
+
+math.inf = float('Inf') #avoid crashing with python2
+
+# initialize weighted graph
+dist = [
+    [0,   1,   2, math.inf],
+    [math.inf, math.inf, math.inf, 1],
+    [math.inf, math.inf, 0,   2],
+    [2, math.inf, math.inf,   0],
+]
+#data structure to store distance vector
+path = defaultdict(defaultdict)
+v = 4 #number of vertices, now it is 4
+#floyd warshall
+for i in range(v):
+    for j in range(v):
+        for k in range(v):
+            # addon code to generate path
+            # else it is just dist[j][k] = min(dist[j][k], dist[j][i] + dist[i][k])
+            val = dist[j][i] + dist[i][k]
+            if dist[j][k] > val:
+                path[j][k] = i
+                dist[j][k] = val
+            else:
+                try:
+                    path[j][k]
+                except:
+                    if dist[j][k] != math.inf:
+                        path[j][k] = k
+            #end addon
+
+# get shortest path's total weight
+def getWeight(g_dist, src, dst):
+    '''
+    type g_dist : 2d Integer weight list
+    type src    : Integer
+    type dst    : Integer
+    '''
+    return g_dist[src][dst]
+    
+
+def getPath(g, src, dst):
+    '''
+        path generator
+        type g   : defaultdict(defaultdict)
+        type src : Integer
+        type dst : Integer
+    '''
+    # pythonic checking of no path since it is a default dict with two level
+    # It should throw error
+    try:
+        g[src][dst]
+    except:
+        return
+    # starting node
+    yield src
+    # all other
+    while src != dst:
+        src = g[src][dst]
+        yield src
+    pass
+
+# result
+print(list(getPath(path, 1, 0)))
+print(getWeight(dist, 1,0))