Add add-piedroconti

algorithms/Python/README.md

@@ -80,6 +80,7 @@
 - [Simple Graph](graphs/graph.py)
 - [BFS SEQUENCE](graphs/bfs-sequence.py)
 - [Depth First Search](graphs/depth-first-search.py)
+  [Dijkstra's algorithm](graphs/dijkstra.py)
 
 ## Trees
 - [Binary Tree](trees/binary_tree.py)

algorithms/Python/graphs/dijkstra.py

@@ -0,0 +1,59 @@
+import heapq
+INF = 10**9
+
+# make graph, set start node
+V, E = map(int, input().split())
+graph = [[]for _ in range(V)] # adjlist
+start = int(input())
+
+# make edges
+for _ in range(E):
+    u, v, w = map(int, input().split())
+    graph[u].append((v, w))    
+
+# make list of distance from start to des, visit status, priority queue
+dist = [INF] * (V)
+visit = [False] * (V)
+PQ = [(0, start)] # cost, vertice
+
+# djikstra algorithm
+while PQ:
+    cost, node = heapq.heappop(PQ)
+    if visit[node]: continue
+    
+    visit[node] = True
+    dist[node] = cost
+    for v, w in graph[node]:
+      alt = cost + w
+      heapq.heappush(PQ, (alt, v))
+
+"""
+SAMPLE INPUT AND OUTPUT
+			___________________________
+			Input:
+			__________
+			<Vertices> <Edges>
+			5 6
+			<start node>
+            0
+			<src node> <des node> <weight>
+			4 0 1
+            0 1 2
+            0 2 3
+            1 2 4
+            1 3 5
+            2 3 6
+			
+			Output:
+			___________
+			Distances from start node 0
+			0
+            2
+            3
+            7
+            INF
+"""
+
+for i in dist:
+  if i == INF: print("INF") 
+  else: print(i)