题目

方法一：常规做法：

class Solution {public String replaceSpace(String s) {int len = s.length() ;StringBuffer str = new StringBuffer();for(int i = 0 ; i < len ; i++){if(s.charAt(i) == ' ') str.append("%20");//遇到空格就在尾部拼接%20else str.append(s.charAt(i));//遇到字符就在尾部正常拼接字符}return str.toString();}
}

方法二：双指针做法

class Solution {public String replaceSpace(String s) {int len = s.length() ;StringBuffer str = new StringBuffer(s);if( len == 0  ) return "";for(int i = 0 ; i< len ; i++)if(s.charAt(i)==' ') str.append("  ");//扩充空间，空格数量2倍String string = str.toString();char[] strs = string.toCharArray();int left = s.length()-1;int right = str.length()-1;while(left >= 0 ){if(str.charAt(left) == ' '){strs[right--] = '0';strs[right--] = '2';strs[right] = '%';}else strs[right] = strs[left];right--;left--;}return new String(strs);}
}