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