Solution to LeetCode ZigZag Conversion problem.

The idea is that that for \(n\) rows, the letters go into rows in this order: \(1, 2, 3, \ldots, n, n-1, n-2, \ldots, 1, 2, \ldots\). Simply make an array, and put each letter into the appropriate slot.

public String convert(String s, int nRows) { if(nRows == 1) return s; String[] res = new String[nRows]; for(int i = 0; i < nRows; i++) res[i] = ""; int ctr = 0; boolean flag = false; for(char c : s.toCharArray()){ res[ctr] += (c + ""); if(ctr == nRows-1 || ctr == 0) flag = !flag; if(flag) ctr++; else ctr--; } String result = ""; for(String ss : res) result += ss; return result; }