/*     * 6. ZigZag Conversion     * 2016-8-26 by Mingyang     * 觉得这个题目面试的必要性不大，有规律，第一行和最后一行每两个相差2n-2     * 中间的每行除了2n-2有外，中间的一个也有2 * (n - 1 - i)     */       public String convert(String s, int numRows) {            if (numRows == 1)                return s;                     StringBuilder sb = new StringBuilder();            // step            int step = 2 * numRows - 2;                     for (int i = 0; i < numRows; i++) {                //first & last rows                if (i == 0 || i == numRows - 1) {                    for (int j = i; j < s.length(); j = j + step) {                        sb.append(s.charAt(j));                    }                //middle rows                    } else {                    int j = i;                    boolean flag = true;                    int step1 = 2 * (numRows - 1 - i);                    int step2 = step - step1;                             while (j < s.length()) {                        sb.append(s.charAt(j));                        if (flag)                            j = j + step1;                        else                            j = j + step2;                        flag = !flag;                    }                }            }                     return sb.toString();        }