006.ZigZag Conversion

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Solution 1:

In this question we need to rearrange a string according to certain order. We need to find out the order of rearrangement.

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public static String convert(String s, int numRows) {
		if (numRows < 2 || s == null || s.length() < numRows)
			return s;
		StringBuilder sb = new StringBuilder();
		int circleLength = 0;
		if (numRows < 3)
			circleLength = numRows;
		else
			circleLength = numRows * 2 - 2;
		for (int i = 1; i <= numRows; i++) {
			for (int j = 1; j <= s.length(); j++) {
				if (j % circleLength == i) {
					sb.append(s.charAt(j - 1));
				}
				
				if (i == 2 && j % circleLength == 0) {
					sb.append(s.charAt(j - 1));
				}
				
				if (i > 2 && i != numRows && j % circleLength == circleLength - i + 2) {
					sb.append(s.charAt(j - 1));
				}
			}
		}
		
		return sb.toString();
	}

Solution 2:

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public String convert(String s, int nRows) {  
	int len = s.length();  
	if (len == 0 || nRows < 2) return s;  
	String ret = "";  
	int lag = 2*nRows - 2; //循环周期  
	for (int i = 0; i < nRows; i++) {  
	    for (int j = i; j < len; j += lag) {  
		ret += s.charAt(j);  
		//非首行和末行时还要加��?��?  
		if (i > 0 && i < nRows-1) {  
		    int t = j + lag - 2*i;  
		    if (t < len) {  
			ret += s.charAt(t);  
		    }  
		}  
	    }  
	}  
	return ret;  
}