Python NearestNeighbor 鄰近算法求解TSP

NearestNeighbor 鄰近算法

輸入：無向連通圖
輸出：TSP路徑

運行環境

• Python3.6
• Numpy 1.17.3

代碼函數說明

• NearestNeighbor(G, label)
• 任選一個城市開始，到達離它最近的城市，然後從該城市出發，選擇離它最近的未訪問過的城市，重複該過程，直到所有城市都被訪問過，再回到開始城市。

代碼實現

import numpy as np

def NearestNeighbor(G, label):
    length = len(G)
    vertices = []
    H = []
    s = np.random.randint(len(G))
    v = s
    while v not in vertices:
        w = 10000003
        index = -1
        for i in range(length):
            if i not in vertices and i != v and G[v][i] < w:
                w = G[v][i]
                index = i
        if w == 10000003 or index == -1:
            break
        H.append((label[v], label[index]))
        vertices.append(v)
        v = index
    return H

G = [
    [0,20,15,35],
    [20,0,10,25],
    [15,10,0,12],
    [35,25,12,0]
]
label = ['a', 'b', 'c', 'd']
result = NearestNeighbor(G, label)
print(result)

無向完全圖

運行結果

運行結果1：
[('a', 'c'), ('c', 'b'), ('b', 'd')]
運行結果2：
[('b', 'c'), ('c', 'd'), ('d', 'a')]
運行結果3：
[('c', 'b'), ('b', 'a'), ('a', 'd')]
運行結果4
[('d', 'c'), ('c', 'b'), ('b', 'a')]