zigzag pattern

Author: u2

src/lib.rs

@@ -5,3 +5,4 @@ pub mod add_two_numbers;
 pub mod length_of_longest_substring;
 pub mod find_median_sorted_arrays;
 pub mod longest_palindrome;
+pub mod zigzag_conversion;

src/zigzag_conversion.rs

@@ -0,0 +1,37 @@
+// What's zigzag pattern?
+// https://discuss.leetcode.com/topic/22925/if-you-are-confused-with-zigzag-pattern-come-and-see
+pub fn zigzag_conversion(string: &str, num: usize) -> String {
+    if num <= 1 { return string.to_string() };
+    let mut res: Vec<Vec<char>> = Vec::with_capacity(num);
+    for _ in 0..num {
+        res.push(Vec::with_capacity(string.chars().count() / num + 1))
+    }
+    let chars = string.chars().into_iter();
+    let mut index: usize = 0;
+    let mut increase: bool = true;
+    for c in chars {
+        res[index].push(c);
+        if increase {
+            index += 1;
+        } else {
+            index -= 1;
+        }
+        if index % (num - 1) == 0 { increase = !increase; }
+    }
+
+    return res.into_iter().map(|i| i.into_iter().collect::<String>() ).collect::<String>();
+}
+
+#[cfg(test)]
+mod test {
+    use super::zigzag_conversion;
+
+    #[test]
+    fn test_zigzag_conversion() {
+        assert_eq!(zigzag_conversion("PAYPALISHIRING", 3), "PAHNAPLSIIGYIR");
+
+        assert_eq!(zigzag_conversion("PAYPALISHIRING", 1), "PAYPALISHIRING");
+
+        assert_eq!(zigzag_conversion("我叫金三顺", 3), "我顺叫三金");
+    }
+}