题目:汇编语言中有一种移位指令叫做循环左移(ROL),现在有个简单的任务,就是用字符串模拟这个指令的运算结果。对于一个给定的字符序列S,请你把其循环左移K位后的序列输出。例如,字符序列S=”abcXYZdef”,要求输出循环左移3位后的结果,即“XYZdefabc”。是不是很简单?OK,搞定它!(剑指offer)
public class stringBuf {
public String LeftRotateString(String str, int n){
if(str.length() == 0) return str;
StringBuffer buffer1 = new StringBuffer(str);
StringBuffer buffer2 = new StringBuffer(str);
StringBuffer buffer = new StringBuffer();
buffer1.delete(0, n);
buffer2.delete(n, str.length());
buffer.append(buffer1.toString()).append(buffer2.toString());
return buffer.toString();
}
public String LeftRotateString2(String str, int n){
if(n<=0) return str;
if(str == null || str.length()==0) return str;
return str.substring(0,n)+str.subSequence(n, str.length());
}
public String leftRetateString3(String str, int n){
if(str.length()==0||n<0) return "";
StringBuffer ab = new StringBuffer(str.substring(0,n));
StringBuffer ab1 = new StringBuffer(str.substring(n,str.length()));
ab1.append(ab);
return ab1.toString();
}
}