**(leetcode_ string) ZigZag Conversion-优快云博客

本文链接：https://blog.youkuaiyun.com/zxasqwedc/article/details/41827303

本文介绍了一种特殊的字符串转换方式——ZigZag模式。该模式将输入字符串按Z形排列并按行读取。文章提供了一个C++实现示例，通过动态调整行数来完成转换。

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ZigZag Conversion

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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：题目有些唬人，其实就是建立nRows个string，然后按照Z的方式一个一个的将字符加到string后面。就是判断是从上往下添加到行还是从下往上添加到行的问题。

class Solution {
public:
    string convert(string s, int nRows) {
        if(nRows==1)    return s; //注意判断
        string *str = new string[nRows];
        int i, row=0;
        bool upToDown = true;
        for(i=0;i<s.length();i++){
            if(upToDown){
               str[row++]+=s[i]; 
               if(row==nRows){
                   upToDown = false;
                   row-=2;
               }  
            }else{
                str[row--]+=s[i];
                if(row==-1){
                    upToDown = true;
                    row+=2;
                }
            }
        }
        string ans;
        for(i=0;i<nRows;i++)
            ans+=str[i];
        return ans;
    }
};