添加top排序

basic_algrithms/sort_algrithms/top.py

@@ -0,0 +1,45 @@
+# 拓扑排序
+def indegree0(v, e):
+    if not v:
+        return None
+    tmp = v[:]
+    # 找出入度为0的节点
+    for i in e:
+        if i[1] in tmp:
+            tmp.remove(i[1])
+
+    if not tmp:
+        return -1
+
+    # 在关系图中标记出入度为0的节点
+    for t in tmp:
+        for i in range(len(e)):
+            if t in e[i]:
+                e[i] = 'useless'
+
+    if v:
+        for t in tmp:
+            v.remove(t)
+    return tmp
+
+
+def top_sort(v, e):
+    result = []
+    while True:
+        nodes = indegree0(v, e)
+        if nodes == -1:
+            print('there\'s a circle.')
+            return
+        elif not nodes:
+            break
+        else:
+            result.extend(nodes)
+    return result
+
+
+if __name__ == '__main__':
+    v = ['a', 'b', 'c', 'd', 'e']
+    e = [('a', 'b'), ('a', 'd'), ('b', 'c'), ('d', 'c'), ('d', 'e'), ('e', 'c')]
+    res = top_sort(v, e)
+    print(res)
+