左旋转字符串

左旋转字符串

字符序列S=”abcXYZdef”

要求输出循环左移3位后的结果

即“XYZdefabc”

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public static String LeftRotateString(String str, int n) {
if (str == null || str.length() == 0 || n < 0) {
return "";
}
StringBuilder sb = new StringBuilder(str);
int len = str.length();
n = n % len;
sb.append(str);
return sb.substring(n, len + n);
}