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6. 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 s, int numRows);
Example 1:
Input: s = "PAYPALISHIRING", numRows = 3 Output: "PAHNAPLSIIGYIR"
Example 2:
Input: s = "PAYPALISHIRING", numRows = 4 Output: "PINALSIGYAHRPI" Explanation: P I N A L S I G Y A H R P I
思路分析
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一刷
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二刷
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/**
* Runtime: 5 ms, faster than 73.81% of Java online submissions for ZigZag Conversion.
*
* Memory Usage: 38.7 MB, less than 77.68% of Java online submissions for ZigZag Conversion.
*
* @author D瓜哥 · https://www.diguage.com
* @since 2019-07-14 18:20
*/
public String convert(String s, int numRows) {
if (Objects.isNull(s) || s.length() == 0) {
return "";
}
if (numRows == 1) {
return s;
}
int length = s.length();
int columnLength = length / numRows;
StringBuilder[] builders = new StringBuilder[numRows];
for (int i = 0; i < builders.length; i++) {
builders[i] = new StringBuilder(columnLength);
}
int direction = 1;
int selector = 0;
char[] chars = s.toCharArray();
for (int i = 0; i < chars.length; i++) {
if (selector == 0) {
direction = 1;
}
if (selector == numRows - 1) {
direction = -1;
}
char aChar = chars[i];
builders[selector].append(aChar);
selector += direction;
}
StringBuilder result = new StringBuilder(length);
for (StringBuilder builder : builders) {
result.append(builder);
}
return result.toString();
}
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/**
* @author D瓜哥 · https://www.diguage.com
* @since 2024-09-18 20:27:18
*/
public String convert(String s, int numRows) {
if (numRows < 2) {
return s;
}
List<StringBuilder> sbs = new ArrayList<>(numRows);
for (int i = 0; i < numRows; i++) {
sbs.add(new StringBuilder());
}
int i = 0, flag = -1;
for (char c : s.toCharArray()) {
sbs.get(i).append(c);
if (i == 0 || i == numRows - 1) {
flag = -flag;
}
i += flag;
}
StringBuilder result = new StringBuilder();
for (StringBuilder sb : sbs) {
result.append(sb);
}
return result.toString();
}