# Problem

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

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``````

# Solution

``````impl Solution {
pub fn convert(s: String, num_rows: i32) -> String {
if num_rows < 2 {
return s;
}
let seq: Vec<char> = s.chars().collect();
let len = seq.len();

let num_rows: usize = num_rows as usize;
let mut i: usize = 0;
let mut j: usize = 0;
let mut step: usize = 0;
let mut row: usize = 0;
let mut down_flag: bool = true;
let mut result = String::with_capacity(s.capacity());

while i < len {
result.push(seq[j]);
i += 1;

if ((row == 0) || (row == (num_rows-1)))
{
step = 2*num_rows-2;
} else {
if (down_flag)
{
step = 2*(num_rows-row)-2;
down_flag = false;
} else {
step = 2*(row+1) - 2;
down_flag = true;
}
}

j += step;
if (j >= len)
{
row += 1;
j = row;
down_flag = true;
}
}

result
}
}``````

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