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# Reverse Integer（翻转整数）

## 翻译

P A H N
A P L S I I G
Y I R

string convert(string text, int nRows);

## 原文

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".

public class Solution
{
public string Convert(string s, int numRows)
{
if (numRows == 1)
return s;
StringBuilder strBuilder = new StringBuilder();
int lengthOfGroup = 2 * numRows - 2;        // 如上图所示，每组的长度为4
for (int row = 0; row < numRows; row++)      // 按从第0行到numRows-1行的顺序遍历
{
if (row == 0 || row == numRows - 1)        // 此处负责第0行和numRows-1行
{
for (int j = row; j < s.Length; j += lengthOfGroup)
{
strBuilder.Append(s[j]);
}
}
else                   // 此处负责第0行和numRows-1行之间的所有行
{
int currentRow = row;           // 在当前行中向右移动（看上图）
bool flag = true;
int childLenOfGroup1 = 2 * (numRows - 1 - row);                //  怎么说呢……中间行的各个索引吧
int childLenOfGroup2 = lengthOfGroup - childLenOfGroup1;

while (currentRow < s.Length)
{
strBuilder.Append(s[currentRow]);
if (flag)
currentRow += childLenOfGroup1;
else
currentRow += childLenOfGroup2;
flag = !flag;
}
}
}
return strBuilder.ToString();
}
}

C++ 的代码肯定是有的：

class Solution {
public:
string convert(string s, int numRows) {
if(numRows==1)
return s;
string str="";
int lengthOfGroup=2*numRows-2;
for(int row=0;row<numRows;row++){
if(row==0||row==numRows-1){
for(int currentRow=row;currentRow<s.length();currentRow+=lengthOfGroup){
str+=s[currentRow];
}
}
else{
int currentRow=row;
bool flag=true;
int childLenOfGroup1=2*(numRows-1-row);
int childLenOfGroup2=lengthOfGroup-childLenOfGroup1;
while(currentRow<s.length()){
str+=s[currentRow];
if(flag)
currentRow+=childLenOfGroup1;
else
currentRow+=childLenOfGroup2;
flag=!flag;
}
}
}
return str;
}
};

public class Solution {
public String convert(String s, int numRows) {
if (numRows == 1)
return s;
StringBuilder strBuilder = new StringBuilder();
int lengthOfGroup = 2 * numRows - 2;
for(int row=0; row < numRows; row++){
if (row == 0 || row == numRows - 1){
for(int currentRow = row; currentRow < s.length(); currentRow += lengthOfGroup){
strBuilder.append(s.charAt(currentRow));
}
}
else{
int currentRow = row;
boolean flag = true;
int childLenOfGroup1 = 2 * (numRows - 1 - row);
int childLenOfGroup2 = lengthOfGroup - childLenOfGroup1;
while (currentRow <s.length()){
strBuilder.append(s.charAt(currentRow));
if (flag)
currentRow += childLenOfGroup1;
else
currentRow += childLenOfGroup2;
flag = !flag;
}
}
}
return strBuilder.toString();
}
}