6. ZigZag Conversion

The string “PAYPALISHIRING” 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 NA P L S I I GY I RAnd then read line by line: “PAHNAPLSIIGYIR"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 = 3Output: “PAHNAPLSIIGYIR"Example 2:Input: s = “PAYPALISHIRING”, numRows = 4Output: “PINALSIGYAHRPI"Explanation:P I NA L S I GY A H RP I难度：medium题目：字符串"PAYPALISHIRING"以之字形表法。思路：数组索引遍历下加上减。Runtime: 22 ms, faster than 80.40% of Java online submissions for ZigZag Conversion.class Solution { public String convert(String s, int numRows) { if (1 == numRows) { return s; } int idx = 0, signFlg = 1; StringBuilder[] sbArray = new StringBuilder[numRows]; for (int i = 0; i < numRows; i++) { sbArray[i] = new StringBuilder(); } for (int i = 0; i < s.length(); i++) { if (0 == idx) { signFlg = 1; } sbArray[idx].append(s.charAt(i)); idx = (idx + signFlg) % numRows; if ((numRows - 1) == idx) { signFlg = -1; } } StringBuilder sb = new StringBuilder(); for (int i = 0; i < numRows; i++) { sb.append(sbArray[i]); } return sb.toString(); }}