Uniform Cost Search, Python 3

Uniform Cost Search

"""
Uniform Cost Search Implementation using PriorityQueue

Map and input taken from
http://www.massey.ac.nz/~mjjohnso/notes/59302/l04.html

Author: Jayesh Chandrapal
Version: 1.0
"""

import queue as Q

def search(graph, start, end):
    if start not in graph:
        raise TypeError(str(start) + ' not found in graph !')
        return
    if end not in graph:
        raise TypeError(str(end) + ' not found in graph !')
        return
    
    queue = Q.PriorityQueue()
    queue.put((0, [start]))
    
    while not queue.empty():
        node = queue.get()
        current = node[1][len(node[1]) - 1]
        
        if end in node[1]:
            print("Path found: " + str(node[1]) + ", Cost = " + str(node[0]))
            break
        
        cost = node[0]
        for neighbor in graph[current]:
            temp = node[1][:]
            temp.append(neighbor)
            queue.put((cost + graph[current][neighbor], temp))
        
def readGraph():
    lines = int( input() )
    graph = {}
    
    for line in range(lines):
        line = input()
            
        tokens = line.split()
        node = tokens[0]
        graph[node] = {}
        
        for i in range(1, len(tokens) - 1, 2):
            # print(node, tokens[i], tokens[i + 1])
            # graph.addEdge(node, tokens[i], int(tokens[i + 1]))
            graph[node][tokens[i]] = int(tokens[i + 1])
    return graph

def main():
    graph = readGraph()
    search(graph, 'Arad', 'Bucharest')
    
if __name__ == "__main__":
    main()
    
"""
Sample Map Input:

14
Arad Zerind 75 Timisoara 118 Sibiu 140
Zerind Oradea 71 Arad 75
Timisoara Arad 118 Lugoj 111
Sibiu Arad 140 Oradea 151 Fagaras 99 RimnicuVilcea 80
Oradea Zerind 71 Sibiu 151
Lugoj Timisoara 111 Mehadia 70
RimnicuVilcea Sibiu 80 Pitesti 97 Craiova 146
Mehadia Lugoj 70 Dobreta 75
Craiova Dobreta 120 RimnicuVilcea 146 Pitesti 138
Pitesti RimnicuVilcea 97 Craiova 138 Bucharest 101
Fagaras Sibiu 99 Bucharest 211
Dobreta Mehadia 75 Craiova 120
Bucharest Fagaras 211 Pitesti 101 Giurgiu 90
Giurgiu Bucharest 90
"""


run \| edit \| history \| help	-1

Taking the given input is resulting into error .Can you suggest something? The error is as follows:

Traceback (most recent call last): File "E:/assignments/ucs.py", line 50, in <module> main() File "E:/assignments/ucs.py", line 46, in main graph = readGraph() File "E:/assignments/ucs.py", line 33, in readGraph line = input() File "<string>", line 1 Arad Zerind 75 Timisoara 118 Sibiu 140 ^ SyntaxError: invalid syntax

by harshita, 3 years ago

This Code is not able to backtrack. Can someone please correct this. I am a beginner in python programming and I don't know how to correct this code. Thanks

by Pavi, 10 months ago

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