541. Reverse String II
2017-09-26 本文已影响0人
namelessEcho
Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and left the other as original.
class Solution {
public String reverseStr(String s, int k) {
StringBuilder sb = new StringBuilder (s);
int len = s.length();
int count = len/(2*k);
int remain = len%(2*k);
if(count>0)
{
for(int i = 0 ;i<count;i++ )
{
int start = 2*k*i;
int end = 2*k*i+k-1;
reverse(sb,start,end);
}
}
if(remain<k)
{
int start =2*k*count;
int end =2*k*count+remain-1;
reverse(sb,start,end);
}
else
{
int start =2*k*count;
int end =2*k*count+k-1;
reverse(sb,start,end);
}
return sb.toString();
}
private void reverse (StringBuilder sb,int start,int end)
{
while(start<=end)
{
char temp = sb.charAt(start);
sb.setCharAt(start,sb.charAt(end));
sb.setCharAt(end,temp);
start++;
end--;
}
}
}