## Weekly Report 2022.08

### 幸福如出一辙，不幸难觅一致

Combine theory and practice: Nothing works and don’t know why.

## Learning

### 旋转图像的两个途径

• reverse upside down, then swap the symmetry
• reverse left to right, then swap the symmetry
/*
* clockwise rotate
* first reverse up to down, then swap the symmetry
* 1 2 3     7 8 9     7 4 1
* 4 5 6  => 4 5 6  => 8 5 2
* 7 8 9     1 2 3     9 6 3
*/
void rotate(vector<vector<int> > &matrix) {
reverse(matrix.begin(), matrix.end());
for (int i = 0; i < matrix.size(); ++i) {
for (int j = i + 1; j < matrix[i].size(); ++j)
swap(matrix[i][j], matrix[j][i]);
}
}

/*
* anticlockwise rotate
* first reverse left to right, then swap the symmetry
* 1 2 3     3 2 1     3 6 9
* 4 5 6  => 6 5 4  => 2 5 8
* 7 8 9     9 8 7     1 4 7
*/
void anti_rotate(vector<vector<int> > &matrix) {
for (auto vi : matrix) reverse(vi.begin(), vi.end());
for (int i = 0; i < matrix.size(); ++i) {
for (int j = i + 1; j < matrix[i].size(); ++j)
swap(matrix[i][j], matrix[j][i]);
}
}


### Centos8 Vault

# CentOS 8
minorver=8.5.2111
sed -e "s|^mirrorlist=|#mirrorlist=|g" \
-e "s|^#baseurl=http://mirror.centos.org/\$contentdir/\$releasever|baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/\$minorver|g" \
-i.bak \
/etc/yum.repos.d/CentOS-*.repo
yum makecache


## Quote

You may be morally and intellectually superior to everybody around you, but don’t try to make it too obvious unless you really intend to irritate somebody.

## Reference

The older I get, the more I realize that most of life is a matter of what we pay attention to, of what we attend to [with focus].
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