tk

The following code works fine. It displays a panedwindow , with a blue box on top and a green box below: panedwindow .root -orient vertical -showhandle true -background red frame .top -background blue -width 100 -height 100 frame .bot -background green -width 100 -height 100 .root add .top .bot pack .root -expand true -fill both However, when I move the panedwindow command down, things stop working. The top, blue box is not shown. Instead, the red of the panedwindow itself shines through: frame .top -background blue -width 100 -height 100 panedwindow .root -orient vertical -showhandle true

题解 [51nod1340]地铁环线 题面 解析 本文参考这篇博客 一开始看到只有120行就打算写一写, 结果一刚就是三个星期 摆摆摆 本来是当查分约束入门学的. step 1 首先来考虑下如果已知总长度 \(s\) 如何判断是否合法. 显然差分约束 对于 \(dis(x,y)>=w\) 这个式子等价于 \(dis[x]+w<=dis[y]\) , 即 \(dis[y]+(-w)>=dis[x]\) . 因此, 若 \(x<y\) ,则 \(y\) 向 \(x\) 连一条边权为 \(-w\) 的边. 若 \(x>y\) ,则 \(y\) 向 \(x\) 连一条边权为 \(s-w\) 的边(要绕一圈,yy一下就知道了). 对于 \(dis(x,y)<=w\) 这个式子就是 \(dis[x]+w>=dis[y]\) . 若 \(x<y\) ,则 \(x\) 向 \(y\) 连一条边权为 \(w\) 的边. 若 \(x>y\) ,则 \(x\) 向 \(y\) 连一条边权为 \(s+w\) 的边. 又因为边权至少为 \(1\) ,即 \(dis[x]+1<=dis[y]\) . \(dis[y]+(-1)>=dis[x]\) . 因此 \(i+1\) 要向 \(i\) 连一条边权为 \(-1\) 的边(n-1要特判) 最后,跑n-1边Bellman_Ford, 若还能进行松弛操作

Following up on this question , I am trying to view (same as in when clicked with left mouse button) a menu, sub1 , when a button, Test , is pressed, but I can't. In the following code button seems to instead freeze the GUI: import tkinter as tk root = tk.Tk() menubar = tk.Menu(root) sub1 = tk.Menu(menubar, tearoff=0) sub1.add_command(label="Item 1", command=lambda : print("item 1")) sub1.add_command(label="Item 2", command=lambda : print("item 2")) menubar.add_cascade(menu=sub1, label="Sub1", underline=0) root.config(menu=menubar) def cb(*args): root.tk.call('::tk::TraverseToMenu', root, 'S')