将一个给定字符串根据给定的行数,以从上往下、从左到右进行 Z 字形排列。
比如输入字符串为 "LEETCODEISHIRING" 行数为 3 时,排列如下:
L C I R
E T O E S I I G
E D H N
之后,你的输出需要从左往右逐行读取,产生出一个新的字符串,比如:"LCIRETOESIIGEDHN"。
请你实现这个将字符串进行指定行数变换的函数:
string convert(string s, int numRows);
示例 1:
输入: s = "LEETCODEISHIRING", numRows = 3
输出: "LCIRETOESIIGEDHN"
示例 2:
输入: s = "LEETCODEISHIRING", numRows = 4
输出: "LDREOEIIECIHNTSG"
解释:
L D R
E O E I I
E C I H N
T S G
思路:随着字符串元素的顺序,它们的行号依次为:0,1,2,3,2,1,0,1,2,3..........规律递增或递减。我们用字符串数组记录答案,第i个字符串代表第i行,最后加起来即可。
class Solution {public String convert(String s, int numRows) {if (numRows == 1) return s;List<StringBuilder> rows = new ArrayList<>();//答案数组for (int i = 0; i < Math.min(numRows, s.length()); i++)rows.add(new StringBuilder());int curRow = 0;boolean goingDown = false;for (char c : s.toCharArray()) {rows.get(curRow).append(c);//到边界就换方向if (curRow == 0 || curRow == numRows - 1) goingDown = !goingDown;if(goingDown)curRow++;else curRow--;}StringBuilder ret = new StringBuilder();for (StringBuilder row : rows) ret.append(row);return ret.toString();}
}