# 6. ZigZag Conversion

### 6. 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"`.

注意i是从0开始的，从1开始就减去1.

```#include <bits/stdc++.h>

#define INF 0x3fffffff
#define eps 1e-8

typedef long long LL;
const double pi = acos(-1.0);
const int mod = 1e9 + 7;
const int maxn = 70;
using namespace std;

string convert(string s, int nRows)
{
if(nRows == 1)return s;
int len = s.size(), k = 0, interval = (nRows<<1)-2;
string res(len, ‘ ‘);
for(int j = 0; j < len ; j += interval)//处理第一行
res[k++] = s[j];
for(int i = 1; i < nRows-1; i++)//处理中间行
{
int inter = (i<<1);//就是i*2，写成位运算是不是高大上一些
for(int j = i; j < len; j += inter)
{
//第一次加的就是字符串第一列的
res[k++] = s[j];
inter = interval - inter;//interval–2*i或者interval-(interval–2*i)=2*i
}
}
for(int j = nRows-1; j < len ; j += interval)//处理最后一行
res[k++] = s[j];
return res;
}

int main()
{
freopen("in.txt","r",stdin);
string ss;
cin>>ss;
cout<<convert(ss, 5);
return 0;
}```

6. ZigZag Conversion

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