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.
Example:
Input: s = "abcdefg", k = 2
Output: "bacdfeg"
Restrictions:
- The string consists of lower English letters only.
- Length of the given string and k will in the range [1, 10000]
class Solution {
public String reverseStr(String s, int k) {
for(int i=0;i<s.length();i+=2*k){
while(i+k>s.length()){
k--;
}
s = s.substring(0,i)+new String(new StringBuffer(s.substring(i,i+k)).reverse())+s.substring(i+k);
}
return s;
}
}class Solution {
public String reverseStr(String s, int k) {
char[] ch = s.toCharArray();
for(int i=0;i<s.length();i+=2*k) {
reverse(ch,i ,i+k);
}
return String.valueOf(ch);
}
private void reverse(char[] ch, int i,int j) {
j = Math.min(ch.length, j)-1;
for(;i<j;i++,j--) {
char temp = ch[i];
ch[i] = ch[j];
ch[j] = temp;
}
}
}