LeetCode ZigZag Conversion

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题目来源：https://leetcode.com/problems/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   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 text, int nRows);

convert("PAYPALISHIRING", 3) should return "PAHNAPLSIIGYIR"

找到规律即可，如上图所示：

假设行数为rows(以0开始）。有两个规律：

1. 第i行以数字i开始

2. 当i为0和rows的时候，两个数字的间隔是2*rows

3. 当i不是0也不是rows的时候，数字间隔是2*(rows-i),2*i

据此写出代码即可：

class Solution {public:string convert(string s, int numRows) {if (numRows<= 1)return s;string rs;for (int i = 0; i < numRows; i++){bool flag = 1;int j = i;while (j < s.size()){rs.push_back(s[j]);if (i == 0 || i == numRows-1)j += (2 * numRows - 2);else{if (flag){j += 2 * (numRows - 1 - i);flag = 0;}else{j += 2 * i;flag = 1;}}}}return rs;}};

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