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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Z字型打印。
public class Solution { public String convert(String s, int numRows) { int len = s.length(); if (len<=numRows||numRows==1){ return s; } int f = 0; StringBuilder ans = new StringBuilder(); for(int j=0;j<numRows;j++){ int l = 0; for(int i=j;i<len;i+=(f==0?2*(numRows-j-1):2*j)){ ans.append(s.charAt(i)); if(j!=0&&j!=numRows-1){ f = 1 - f; } if(l==0){ f = 0; l = 1; } if(j==numRows-1){ f = 1; l = 1; } if(ans.length()==s.length()){ break; } } } return ans.toString(); } }tips：一定记得用StringBuilder！ 相同的程序，使用String耗时128ms，stringbuilder加速一倍以上