【leetcode刷题笔记】Simplify Path

Given an absolute path for a file (Unix-style), simplify it.

For example,
path = "/home/", => "/home"
path = "/a/./b/../../c/", => "/c"

Corner Cases:

• Did you consider the case where path = "/../"?
  In this case, you should return "/".
• Another corner case is the path might contain multiple slashes '/' together, such as"/home//foo/".
  In this case, you should ignore redundant slashes and return "/home/foo".

---

题解：

1. 用split函数将path按照一个或者多个（正则表达式实现）'/'分成不同的字符串存放在数组positions中。
2. 遍历positions，如果遇到非"..",".",""的字符串，就放入answers列表中；如果遇到".."且answers不为空，就把answers尾部的字符串扔掉。
3. 最后把answers中的字符串用"/"连接起来，注意在连接后的字符串结尾会多一个"/'，可以substring一下result去掉。

代码如下：

public class Solution {
    public String simplifyPath(String path) {
        ArrayList<String> answers = new ArrayList<String>();
        String[] positions = path.split("/+");
        for(int i = 0;i < positions.length;i++){
            if(positions[i].equals("..")){
                if(answers.size() > 0)
                    answers.remove(answers.size()-1);
            }
            else if(!positions[i].equals(".") && !positions[i].equals(""))
            {
                answers.add(positions[i]);
            }
        }
        
        String result = new String("/");
        for(String s:answers)
            result += s + "/";
        
        if(result.length() > 1)
            result = result.substring(0,result.length()-1);
        
        return result;
    }
}