6. Zigzag Conversion

The string `"PAYPALISHIRING"` is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

```P   A   H   N
A P L S I I G
Y   I   R
```

And then read line by line: `"PAHNAPLSIIGYIR"`

Write the code that will take a string and make this conversion given a number of rows:

```string convert(string s, int numRows);
```

Example 1:

```Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"
```

Example 2:

```Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P     I    N
A   L S  I G
Y A   H R
P     I
```

Example 3:

```Input: s = "A", numRows = 1
Output: "A"
```

Constraints:

• `1 <= s.length <= 1000`
• `s` consists of English letters (lower-case and upper-case), `','` and `'.'`.
• `1 <= numRows <= 1000`

6. Zigzag Conversion
``````struct Solution;

impl Solution {
fn convert(s: String, num_rows: i32) -> String {
let mut res = "".to_string();
let n = num_rows as usize;
if n == 1 {
return s;
}
let m = s.len();
let mut v: Vec<String> = vec!["".to_string(); n];
let mut row = 0;
let mut direction = true;
for j in 0..m {
v[row] += &s[j..=j];
if row == 0 {
direction = true;
row += 1;
} else if row == n - 1 {
direction = false;
row -= 1;
} else {
if direction {
row += 1;
} else {
row -= 1;
}
}
}
for t in v {
res += &t;
}
res
}
}

#[test]
fn test() {
let s = "PAYPALISHIRING".to_string();
let num_rows = 3;
let res = "PAHNAPLSIIGYIR".to_string();
assert_eq!(Solution::convert(s, num_rows), res);
let s = "PAYPALISHIRING".to_string();
let num_rows = 4;
let res = "PINALSIGYAHRPI".to_string();
assert_eq!(Solution::convert(s, num_rows), res);
let s = "AB".to_string();
let num_rows = 1;
let res = "AB".to_string();
assert_eq!(Solution::convert(s, num_rows), res);
}
``````