[leetcode] 6. ZigZag Conversion

题目链接：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 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 text, int nRows);

convert(“PAYPALISHIRING”, 3) should return “PAHNAPLSIIGYIR”.

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思路

举个栗子：abcdefghijklmn 4

a g m

b f h l n

c e i k

d j

然后我们要给出的答案就是agmbfhinceikdj，横着读。

思路就是有几行就申请几个字符串，然后一个字符串把一行的字符收集起来，最后再加在一起。关于之字形遍历我们可以设置一个递增标记flag，可以为1和-1，代表下一个是增加还是减小。

class Solution {public:    string convert(string s, int numRows) {        if(numRows <= 1) return s;        vector<string> strs(numRows,"");        string ans;        int i = -1,flag = 1,k = 0;        while(++i < s.size()){            strs[k] += s[i];            k += flag;            if(k == -1) k = 1,flag = 1;            else if(k == numRows) k = numRows - 2,flag = -1;        }        for(auto str: strs) ans += str;        return ans;    }};