1. we can pass parameter into `./make` instead of using `sed` to modify the file,
`-jn` can be passed although `-j n` can't.
2. we can install the executable file into PATH instead of throwing it into home dir.
the result of git blame: https://github.com/OI-wiki/OI-wiki/commit/
47acc594f2d94423d319a7b1ee83546ad29552a6
```bash
sudo apt update
sudo apt install qt5-default build-essential git -y
-git clone --depth=1 http://github.com/menci/lemon.git
+git clone --depth=1 https://github.com/Menci/Lemon.git
cd lemon
-# 可以修改 make 文件来调整 make job 的线程数
-sed -i 's/make $/make -j 1 $/g' make
-./make
-cp Lemon ~
-cd ..
+# 可以修改 -j 后面的数字来调整 make job 的线程数
+./make -j2
+sudo install -Dm755 -t /usr/bin/ Lemon
```
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