zigzag-conversion solution java

zigzag-conversion/Solution.java

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+// Accepted
+// Runtime: 4 ms
+// Memory Usage: 39.8 MB
+// Submitted: January 13th, 2021
+
+class Solution {
+    public String convert(String s, int numRows) {
+        if (numRows == 1)
+            return s;
+        
+        // Declare and instantiate with empty strings
+        StringBuilder[] levels = new StringBuilder[numRows];
+        for (int i = 0; i < levels.length; i++)
+            levels[i] = new StringBuilder();
+        
+        int j = 1; // Start at 1 decrementing since it moves forward immediately before recording
+        boolean direction = false; // true = increment, false = decrement
+        for (int i = 0; i < s.length(); i++) {
+            // If hitting the top or bottom, set direction accordingly
+            if (j == 0)
+                direction = true;
+            else if (j == numRows - 1)
+                direction = false;
+        
+            // Increment or decrement based on the direction
+            j += direction ? 1 : -1;            
+            levels[j].append(s.charAt(i));
+        }
+        
+        StringBuilder compile = new StringBuilder();
+        for (StringBuilder level : levels) {
+            compile.append(level);
+        }
+        return compile.toString();
+    }
+}