leetcode-algorithms/src/ZigZagConversion.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

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

// T: O(|s|)

// S: O(|s|)

public class ZigZagConversion {

public static String convert(String s, int numRows) {

if (numRows == 1) return s;

final StringBuilder result = new StringBuilder();

final int jumpSize = (numRows - 1) * 2;

// first row

for (int i = 0 ; i < s.length() ; i += jumpSize) {

result.append(s.charAt(i));

}

for (int row = 1 ; row < numRows - 1 ; row++) {

int[] jumps = {jumpSize - 2 * row, 2 * row};

for (int i = row, k = 0 ; i < s.length() ; k ^= 1) {

result.append(s.charAt(i));

i += jumps[k];

}

// last row

for (int i = numRows - 1 ; i < s.length() ; i += jumpSize) {

result.append(s.charAt(i));

}

return result.toString();

}

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