Leetcode第六题—— ZigZag Conversion（字符串的之字形转换）
题目描述：
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 N
A P L S I I G
Y I R
And 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 = 3
Output: "PAHNAPLSIIGYIR"
Example 2:
Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P I N
A L S I G
Y A H R
P I
My Solution（19ms，38.4MB）
比较容易想到的一个办法，用一个二维数组按照之字形储存起来，然后逐行逐列地去读取，然后拼接成一个字符串。
class Solution { public String convert(String s, int numRows) { if(numRows<2){return s;}//防止除数为零 int index = 0,row=numRows-2; int columns = s.length()/(2*numRows-2)*(numRows-1);//columns实际上是指二维数组列下表的最大值 int remainder = s.length()%(2*numRows-2); if(remainder>numRows){columns = remainder - numRows + columns;} String[][] zigzag = new String[numRows][columns+1]; //开始逐行填充数组 for(int j = 0;j<columns+1;j++){ if(j%(numRows-1)==0){//竖笔 for(int i = 0;i<numRows;i++){ if(index<s.length()){ zigzag[i][j] = s.substring(index,index+1);index++; row = numRows-2; } } }else{ if(index<s.length()){ zigzag[row][j] = s.substring(index,index+1);index++; row--; } } } 开始拼接结果字符串 String result = ""; for(int i =0 ; i<numRows ;i++){ for(int j=0;j<columns+1;j++){ if(zigzag[i][j]!=null){ result = result + zigzag[i][j]; } } } return result; } }