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  • [leetcode] 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".

    https://oj.leetcode.com/problems/zigzag-conversion/

    思路:找规律。每个zigzag是2*rows-1个字符。

    public class Solution {
    	public String convert(String s, int nRows) {
    		if (nRows == 1)
    			return s;
    		StringBuilder sb = new StringBuilder();
    		int len = s.length();
    		for (int i = 0; i < nRows; i++) {
    			if (i == 0 || i == nRows - 1) {
    				int j = i;
    				while (j < len) {
    					sb.append(s.charAt(j));
    					j += 2 * nRows - 2;
    				}
    			} else {
    				int j = i;
    				int k = 2 * nRows - 2 - i;
    				while (j < len || k < len) {
    					if (j < len)
    						sb.append(s.charAt(j));
    					if (k < len)
    						sb.append(s.charAt(k));
    					j += 2 * nRows - 2;
    					k += 2 * nRows - 2;
    				}
    			}
    
    		}
    		return sb.toString();
    
    	}
    
    	public static void main(String[] args) {
    		System.out.println(new Solution().convert("PAYPALISHIRING", 3));
    		System.out.println(new Solution().convert("abcdefghijklmn", 5));
    		System.out.println(new Solution().convert("abcdefghijklmn", 4));
    		System.out.println(new Solution().convert("abcdefghijklmn", 1));
    
    	}
    
    }

    第二遍记录:比较无聊的数学题,关键在于推算坐标。坐标分为两种,一种是竖直的,一种是斜向的。建议多画集中情况具体分析下。 

    参考:

    http://fisherlei.blogspot.com/2013/01/leetcode-zigzag-conversion.html

    http://blog.csdn.net/linhuanmars/article/details/21145039

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  • 原文地址:https://www.cnblogs.com/jdflyfly/p/3810675.html
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