From 2f046e00bd00c9506c3d596eba186f8a5f4d769e Mon Sep 17 00:00:00 2001
From: Saksham Agarwal <skshamagarwal@gmail.com>
Date: Fri, 1 Oct 2021 14:47:52 +0530
Subject: [PATCH] Dijkstra Algorithm

---
 Algorithms/Algorithms/Dijkstra/Dijkstra.py | 72 ++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 Algorithms/Algorithms/Dijkstra/Dijkstra.py

diff --git a/Algorithms/Algorithms/Dijkstra/Dijkstra.py b/Algorithms/Algorithms/Dijkstra/Dijkstra.py
new file mode 100644
index 0000000..41a74d7
--- /dev/null
+++ b/Algorithms/Algorithms/Dijkstra/Dijkstra.py
@@ -0,0 +1,72 @@
+# graph = [1, 2, 3, 4, 5, 6]
+# adjacents = [[2, 3], [1, 3, 4, 4], [1, 2, 4, 5], [2, 2, 3, 5, 6], [3, 4, 6], [4, 5]]
+# weights = [[7, 8], [7, 3, 6, 8], [8, 3, 4, 3], [6, 8, 4, 2, 5], [3, 2, 2], [5, 2]]
+
+# Q's graph
+graph = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']
+
+adjacents = [['b', 'h'], ['h', 'c'],
+             ['d', 'i', 'f'], ['e', 'f'],
+             ['f'], ['g'], ['i', 'h'],
+             ['i'], []]
+
+weights = [[4, 8], [11, 8],
+           [7, 2, 4], [6, 14],
+           [10], [2], [6, 1],
+           [7], []]
+
+
+visited = []
+parent = [0] * len(graph)
+cost = [-1] * len(graph)
+
+# Element to start from
+x = 'a'
+
+# Until all Nodes are visited
+for _ in range(len(graph)):
+    visited.append(x)
+    # print(f"Vertex = {x}")
+    index_x = graph.index(x)
+    for i in range(len(adjacents[index_x])):
+
+        if adjacents[index_x][i] not in visited:
+            index_adj = graph.index(adjacents[index_x][i])
+
+            # Cost Update
+            if cost[index_adj] == -1 or cost[index_adj] > weights[index_x][i] + cost[index_x]:
+                if cost[index_x] != -1:
+                    cost[index_adj] = cost[index_x] + weights[index_x][i]
+                    parent[index_adj] = x
+                else:
+                    cost[index_adj] = weights[index_x][i]
+                    parent[index_adj] = x
+
+            else:
+                pass
+        # print(f"Cost = {cost}")
+        # print(f"Parent{parent}")
+        # print("\n")
+
+    # Minimum Value of list Cost from non-visited nodes
+    min = -1
+    for i in range(len(cost)):
+        if graph[i] in visited or cost[i] == -1:
+            pass
+        elif min == -1 or min > cost[i]:
+            min = cost[i]
+            index_min = i
+
+    # Shifting to Next Node
+    x = graph[index_min]
+
+# print("\n")
+# print("Visited List {:>20}".format(str(visited)))
+# print("Final Cost {:>23}".format(str(cost)))
+# print("Parents {:>25}".format(str(parent)))
+cost[0] = 0
+print("-------------------------------\n")
+print("Shortest Path - Dijkstra\n")
+for i in range(1, len(cost)):
+    print(f"Cost a to {graph[i]} = {cost[i]}")
+print("\n-----------------------------")
\ No newline at end of file