题目:

Given an absolute path for a file (Unix-style), simplify it.
For example,
path = "/home/", => "/home"
path = "/a/./b/../../c/", => "/c"

分析:

路径化简。

基本思路就是使用栈来模拟进入某一路径或者返回上一级。

注意以下边界情况：

"/../" 应化简为 "/"
"/home//foo/" 应化简为 "/home/foo"

代码:

Java

public class Solution {
	
	public String simplifyPath(String path) {
    	StringBuilder sb = new StringBuilder();
        Stack<String> stack = new Stack<String>();
        for(int i = 1, prevSlash = 0; i <= path.length(); i++){
        	if(i == path.length() || path.charAt(i) == '/'){
        		String folder = path.substring(prevSlash + 1, i);
        		prevSlash = i;
        		if(folder.equals("..")){
            		if(!stack.isEmpty()) stack.pop();
            	}
            	else if(!folder.equals(".") && folder.length() > 0)
            		stack.push(folder);
        	}
        }
        while(!stack.isEmpty()) sb.insert(0, "/" + stack.pop());
        return sb.length() == 0 ? "/" : sb.toString();
    }
}