resolve aylei#6

Author: aylei

src/lib.rs

@@ -3,3 +3,4 @@ mod n0002_add_two_numbers;
 mod n0003_longest_substring;
 mod n0004_median_of_two_sorted_arrays;
 mod n0005_longest_palindromic_substring;
+mod n0006_zigzag_conversion;

src/n0006_zigzag_conversion.rs

@@ -0,0 +1,86 @@
+/**
+ * [6] ZigZag Conversion
+ *
+ * The string <code>"PAYPALISHIRING"</code> 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: <code>"PAHNAPLSIIGYIR"</code>
+ * 
+ * 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
+ * 
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+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 unit: usize = (2 * num_rows - 2) as usize;
+        let mut sb = String::with_capacity(s.capacity());
+        for row in 0..num_rows {
+            let mut i = row as usize;
+            let step1 = 2 * (num_rows - 1 - row) as usize;
+            let step2 = (unit - step1) as usize;
+            let mut trigger = false;
+            while i < len {
+                sb.push(seq[i]);
+                if step1 == 0 {
+                    i += step2
+                } else if step2 == 0 {
+                    i += step1
+                } else {
+                    i += if trigger { step2 } else { step1 };
+                    trigger = !trigger;
+                }
+            }
+        }
+        sb
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_6() {
+        assert_eq!(Solution::convert("PAYPALISHIRING".to_string(), 4), "PINALSIGYAHRPI");
+        assert_eq!(Solution::convert("PAYPALISHIRING".to_string(), 3), "PAHNAPLSIIGYIR");
+        assert_eq!(Solution::convert("A".to_string(), 1), "A");
+        assert_eq!(Solution::convert("AY".to_string(), 2), "AY");
+    }
+}