What is Leetcode?

What is Leetcode?
Leetcode is an online platform to enhance your skills and prepare for tech interviews.
There site has over 1900 coding problems with questions to help you prepare.

Samsung A31 does not turn on after system update

1. Press volume down button + power button at same time for at least 10 seconds, release buttons when you see phone Logo and let it finish booting up.
2. If it still does not work, try a few more times, if it still does not work, try:
3. Plug in power cable and charge for a while, no matter battery sign shows or not. then with power cable plugged in, try step 1

Windows 10 stuck freeze in cold start bootup

solution:
Search "Sleep settings" in Windows search bar at bottom left of window,
in search results, click "Power & sleep settings" , then click "Additional power settings" in right pane
click "Choose what the power buttons do" at left pane
click the link "Change settings that are currently unavailable"
uncheck the "Turn on fast startup (recommended)", click "Save changes" button

How to manually clean up Android phone before selling it

Ideally to clean up a phone is do factory reset after you backed up all data. If for some reason you do not want to do factory reset, this is items to consoder to do manually:
Connect to PC with USB cable in File transfer mode (find in notifications on phone after plug in to PC)
cut & paste all pictures to backup PC
cut & paste all downloads to backup PC
cut & paste all voice recordings to backup PC
uninstall all user installed apps

the following 3 items, you'd better transfer data to your new phone or backed up in google account or backed up by an app tool:
delte all call logs
delete all messages
delete all contacts

format SD on SD card reader
remove google accounts
remove screen password

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Sign up for free to get 5000LRC trial fund, you just need to complete level 1 identity verification(email, country of residence, SMS verification),
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Disclaimer: Any investment has risk, play at your own risk.

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Freephoneline incoming calls no ringing

My Freephoneline has been working well for years, but recently no ringing for incoming calls, but calling out is OK.

I have not made any changes myself, I guess either freephoneline side has changed something, or due to my router firmware automatic updates.

1. Tried some solutions from online, like on VOIP adapter, change SIP proxy to voip2.freephoneline.ca or voip4.freephoneline.ca:6060 and change SIP port to 6060, did not work.

2. On router, disable SIP ALG did not work.

3. Fixed, ended up these changes, everything else keep original setting from Fongo when first time purchased:

a) on router, disabled SIP ALG

b) on router, added port forwarding for the following:

UDP Ports: 5060-5061, 6060-6061, 13000-13001,16384-16482

My router is Hitron CGNM-2250, followed:

its default IP is 192.168.0.1, from a browser, access that IP, login (user name, password should be on a label on the box), click Basic tab from top,

then click Port Forwarding tab from second row from top.

click Add Rule button from botton

Common Application field, leave as default

Create a name for this forward and type it into the Application Name box. Since the name does not have an effect on the functionality of the forward,

choose a name that will help you remember why the forward was created.

Go ahead and enter the port number into the left Public Port and the right Public Port boxes, to forward a single port. To forward a range of ports,

enter the lowest number of that range into the left Public Port box and then enter the highest number of that range into the right Public Port box.

Take the values that you entered in the Public Port boxes and put the exact same numbers in the Private Port boxes.

Use the Protocol dropdown box choose UDP.

You need to enter the VOIP adapter IP address that you are forwarding ports to into the Local IP Address box.

Make sure that Remote IP Address is set to Any.


Make the Enabled selection in the Status drop-down list.

When you are completely finished, click the Apply button at the bottom of the page to apply these changes.

c) On VOIP Adaper, STUN server: changed from stun.xten.com to stun.l.google.com:19302 (not sure if it is necessary, but seems it did not harm)

d) Connect the phone directly to ATA instead of household wiring.

all of above changes are not reliable. ended up buying a Grandstream HT802, followed guide here to configure, https://forum.fongo.com/viewforum.php?f=15 , everything back to normal.