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LeftRotateString.java
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34 lines (28 loc) · 853 Bytes
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package _58;
public class LeftRotateString {
/**
* 实现一个函数完成字符串的左旋转功能。比如，输入 abcdefg 和数字 2，输出为 cdefgab。
*/
public static String leftRotateString(String str, int k) {
int n = str.length();
k = k % n;
if (k == 0) {
return str;
}
StringBuilder sb = new StringBuilder(str);
reverse(sb, 0, k - 1);
reverse(sb, k, n - 1);
reverse(sb, 0, n - 1);
return sb.toString();
}
public static void reverse(StringBuilder sb, int start, int end) {
for(int i = start; i <= start + (end - start)/2; i++) {
char temp = sb.charAt(i);
sb.setCharAt(i, sb.charAt(end - i + start));
sb.setCharAt(end - i + start, temp);
}
}
public static void main(String[] args) {
System.out.println(leftRotateString("abcdefg", 2));
}
}