```
public class Solution {
public String convert(String s, int numRows) {
if(numRows < 1) {
return "";
} else if (numRows == 1) {
return s;
} else {
int divide = numRows*2 - 2;
StringBuilder result = new StringBuilder();
int length = s.length();
for (int j = 0; j < numRows; j++) {
int count = 1;
if (j == 0 || j == numRows - 1) {
for (int i = j; i < length; i += divide) {
result.append(s.charAt(i));
}
} else {
for (int i = j; i < length; ) {
result.append(s.charAt(i));
i = count * divide - i;
count++;
}
}
}
return result.toString();
}
}
}
```