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Rotation.java
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58 lines (53 loc) · 1.64 KB
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package strings;
/**
* Given a string, moving several characters in front of the string to the end of the string. For
* example, move the two characters'a' and 'b' in front of the string "abcdef" to the end of the
* string, so that the original string becomes the string "cdefab"
*/
public class Rotation {
public static void main(String[] args) {
assert rotation("abcdef", 2).equals("cdefab");
char[] values = "abcdef".toCharArray();
rotation(values, 2);
assert new String(values).equals("cdefab");
}
/**
* Move {@code n} characters in front of given string to the end of string time complexity: O(n)
* space complexity: O(n)
*
* @param s given string
* @param n the total characters to be moved
* @return string after rotation
*/
public static String rotation(String s, int n) {
return s.substring(n) + s.substring(0, n);
}
/**
* Move {@code n} characters in front of given character array to the end of array time
* complexity: O(n) space complexity: O(1)
*
* @param values given character array
* @param n the total characters to be moved
*/
public static void rotation(char[] values, int n) {
reverse(values, 0, n - 1);
reverse(values, n, values.length - 1);
reverse(values, 0, values.length - 1);
}
/**
* Reverse character array
*
* @param values character array
* @param from begin index of given array
* @param to end index of given array
*/
public static void reverse(char[] values, int from, int to) {
while (from < to) {
char temp = values[from];
values[from] = values[to];
values[to] = temp;
from++;
to--;
}
}
}