Leetcode 6--ZigZag Conversion

The string is "PAYPALISHIRING" written with 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 on line:"PAHNAPLSIIGYIR"

Write the code that would take a string and make this conversion given a number of rows:

String convert (string text, int nRows);

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

Oneself come up not to understand what is zigzag, also thought is more in the point, the result is not right, make quite complex, right vote paste code, when a lesson:

1  Public classzigzagconversion {2      Public StaticString Convert (String s,intnumrows) {3         if(s = =NULL|| S.length () = = 0)4             returns;5         if(NumRows < 2)6             returns;7         intGap = NumRows-2;8String res = "";9 Ten          for(inti = 0; i < numrows; i++) { One             if(i = = 0) { A                  for(intj = i; J < S.length (); J + = (NumRows * 2-2)) -Res + =S.charat (j); -}Else if(i = = NumRows-1) { the                  for(intj = i; J < S.length (); J + = (NumRows * 2-2)) -Res + =S.charat (j); -}Else { -                  for(intj = i; J < S.length (); J + = (NumRows * 2-2)) { +Res + =S.charat (j); -                     if(j + numrows * 2-3-i <s.length ()) +Res + = S.charat (j + numrows * 2-3-i); A                 } at             } -         } -  -         returnRes; -     } -  in      Public Static voidMain (string[] args) { -String s = "ABCDE"; toString res = CONVERT (S, 4); + System.out.println (res); -     } the  *}

Problem code, boundary problem not solved well

1  Public classSolution {2      PublicString Convert (String s,intnRows) {3         if(s = =NULL|| S.length () <= NRows | | NRows <= 1)returns;4StringBuffer SB =NewStringBuffer ();5         //The first row6          for(inti = 0; I < s.length (); i + = (nRows-1) * 2) {7 Sb.append (S.charat (i));8         }9         Ten          for(inti = 1; i < nRows-1; i++) { One              for(intj = i; J < S.length (); j+= (nRows-1) * 2) { A Sb.append (S.charat (j)); -                 if(j + (Nrows-i-1) * 2 <s.length ()) { -Sb.append (S.charat (j + (Nrows-i-1) * 2)); the                 } -             } -         } -         //The last row +          for(inti = nRows-1; I < s.length (); i + = (nRows-1) * 2) { - Sb.append (S.charat (i)); +         } A         returnsb.tostring (); at     } -}

Baidu later, see others code is quite concise, Fang know that they did not understand the topic.

Zigzag: That is, the cyclic diagonal structure (

0				8				16
1			7	9			15	17
2		6		10		14		18
3	5			11	13			19
4				12				20

）

Constructs n strings, loops each to add the corresponding characters, and finally merges all the characters;

I re-wrote according to the idea:

1  Public classzigzagconversion {2      Public StaticString Convert (String s,intnumrows) {3         if(s = =NULL|| S.length () = = 0)4             returns;5         if(NumRows < 2)6             returns;7string[] Res =NewString[numrows];8String result = "";9         Ten         inti = 0, J; One  A          while(I <s.length ()) { -              for(j = 0; J < numrows && I < S.length (); j + +) { -RES[J] + =S.charat (i); thei++; -             } -              for(j = numRows-2; J > 0 && I < s.length (); j--) { -RES[J] + =S.charat (i); +i++; -             } +         } A          for(intk = 0; K < numrows;k++) atResult + =Res[k]; -         returnresult; -     } -  -      Public Static voidMain (string[] args) { -String s = "paypalishiring"; inString res = CONVERT (S, 3); - System.out.println (res); to     } +}

Just not once the string array is initialized to null by default, how the overwrite has not been resolved, the original text in C + + code is as follows:

1 stringConvertstringSintnRows) {2     if(NRows = =1)returns;3     stringRes[nrows];4     inti =0, J, Gap = nrows-2;5      while(I <s.size ()) {6          for(j =0; I < S.size () && J < NRows; ++J) res[j] + = s[i++];7          for(j = gap; I < S.size () && J >0; --J) res[j] + = s[i++];8     }9     stringstr ="";Ten      for(i =0; i < nRows; ++i) Onestr + =Res[i]; A     returnstr; -}

Find some of their own problems: the first is not very good to think about the problem, or that their ideas are always some deviation, followed by the boundary problem, always make small mistakes.

Leetcode 6--ZigZag Conversion