一道小学数学题（ZigZag Conversion） LeetCode

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);

【一道小学数学题（ZigZag Conversion）】通俗一点来说，就是将给定字符串以N字形输出之后再去掉空格回车按行顺序得到一个全新的字符串。
来看几个例子：

Example 1: Input: s = "PAYPALISHIRING", numRows = 3 Output: "PAHNAPLSIIGYIR" ---Example 2: Input: s = "PAYPALISHIRING", numRows = 4 Output: "PINALSIGYAHRPI" Explanation: PIN AL SI G Y AH R PI

求解算法一开始没有注意到要去掉空格，发现之后全都注释掉对应部分就过了。思路很简单，就是发现规律而已。

class Solution { public: string convert(string s, int numRows) { if (numRows == 1) { return s; } int L = s.length(); int a = L/(2*numRows-2), b = L%(2*numRows-2); int numCols = a*(numRows-1)+1+b/numRows*(b%numRows); string ss = ""; int index = 0; for (int i = 0; i < numRows; i++) { for (int j = 0; j < numCols; j++) { a = j%(numRows-1); if (a > 0 && a+i != numRows-1) { //ss += " "; } else { b = j/(numRows-1); index = b*(2*numRows-2)+(a==0?i:numRows+a-1); if (index < s.length()) { ss += s[index] ; } /*else { ss += ' '; }*/ } } //ss += '\n'; } return ss; } };