ATRS punch tenth week

1.Algorithm

　　https://leetcode-cn.com/problems/merge-two-sorted-lists/

　　

Method 1: Recursive

idea

We can recursively define the following two lists in the  merge operation (ignoring border situations, such as empty list, etc.):

\left\{ \begin{array}{ll} list1[0] + merge(list1[1:], list2) & list1[0] < list2[0] \\ list2[0] + merge(list1, list2[1:]) & otherwise \end{array} \right.{list1[0]+merge(list1[1:],list2)list2[0]+merge(list1,list2[1:])​list1[0]<list2[0]otherwise​

In other words, two lists with the rest of the head of a smaller element of  merge the operating results of the merger.

We directly above recursive algorithm process modeling, first consider the boundary conditions. Special, if  l1 or  l2 beginning  null , so there is no need to merge operations, so we only need to return a non-empty list. Otherwise, we have to determine  l1 and  l2 which elements of the head is smaller, then recursively down a decision in the value added to the result. If the two lists are empty, then the process terminates, so recursive process will eventually terminate.

class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if (l1 == null) {
            return l2;
        }
        else if (l2 == null) {
            return l1;
        }
        else if (l1.val < l2.val) {
            l1.next = mergeTwoLists(l1.next, l2);
            return l1;
        }
        else {
            l2.next = mergeTwoLists (L1, l2.next);
            return l2;
        }

    }
}

2.Review

　　https://link.medium.com/qNt4XAqc0W

3.Tips　　

　　

@PostMapping("/multiUpload")
@ResponseBody
public String multiUpload(HttpServletRequest request) {
    List<MultipartFile> files = ((MultipartHttpServletRequest) request).getFiles("file");
    String filePath = "/Users/itinypocket/workspace/temp/";
    for (int i = 0; i < files.size(); i++) {
        MultipartFile file = files.get(i);
        if (file.isEmpty()) {
            return "Uploading" + (i ++) + "files failed";
        }
        String fileName = file.getOriginalFilename();

        File dest = new File(filePath + fileName);
        try {
            file.transferTo ();
            LOGGER.info ( "first" + (i + 1) + "files uploaded successfully");
        } catch (IOException e) {
            LOGGER.error(e.toString(), e);
            return "Uploading" + (i ++) + "files failed";
        }
    }

    return "Upload successful";

}

　　

4.Share

　　https://www.cnblogs.com/tanshaoshenghao/p/10924205.html

　　Javah constant pool data to frequently used into the memory to avoid repetition of creation and destruction, data sharing, improve system performance.

　　From jdk1.7, the string constant pool is implemented in the Java heap memory

　　String s1 = "hello"; String s2 = new String("hello");

　　s1 is to go find the constant pool, if not back into the constant pool in the new, s2 direct new without the constant pool.

　　String s1 = new String("hello ") + new String("world");

　　Now the heap create two objects, spliced ​​using stringBuilder, and then generate a new object variable s1 point to the new object "hello world".

　　s1.intern ();

　　This is to query whether the string constant pool if there is no direct return, the variable is registered in the constant pool, and back again.

　　String s1 = "hello "; String s2 = "world"; String s3 = s1 + s2; String s4 = "hello world"; System.out.println(s3 == s4);

　　s3 is an object with the new splicing stringbuilder so s3! = s4