Dijkstra algorithm.

dijkstra.py

nodes = {
    "A": ["", ""],
    "B": ["", ""],
    "C": ["", ""],
    "D": ["", ""],
}

connects = [
    ["A", "B", "10"],
    ["B", "C", "10"],
    ["C", "D", "10"],
    ["A", "D", "31"],
]

start = "A"
goal = "D"

def initStart(start):
    nodes[start] = [start, 0]

def nodeTo(base):
    loopCount = 0

    for connect in connects:
        loopCount += 1
        if connect[0] == base:
            target = connect[1]
            currentCost = int(nodes[base][1])
            rootCost = int(connect[2])
            if nodes[target][0] == "" or int(nodes[target][1]) > currentCost + rootCost:
                nodes[target][0] = base
                nodes[target][1] = str(currentCost + rootCost)

                loopCount += nodeTo(target)
    return loopCount


initStart(start)
print nodeTo(start)
print nodes

print "=" * 30
print nodes[goal][1]
print "=" * 30