How do you get the day from Date and Time?

Problem statement:
You are given a date. You just need to write the method, , which returns the day on that date.
For example, if you are given the date August 14th 2017 the method should return MONDAY as the day on that date.

1. public static String findDay(int mm, int dd, int yy) 
2. {
3. java.time.LocalDate dt = java.time.LocalDate.of(yy, mm, dd);
4. return dt.getDayOfWeek().name();
5. }

Output: MONDAY

How do you solve problem based on Counting Valleys?

Problem statement:
Gary is an avid hiker. He tracks his hikes meticulously, paying close attention to small details like topography. During his last hike he took exactly n steps. For every step he took, he noted if it was an uphill, U, or a downhill, D step. Gary's hikes start and end at sea level and each step up or down represents a 1 unit change in altitude. We define the following terms:

• A mountain is a sequence of consecutive steps above sea level, starting with a step up from sea level and ending with a step down to sea level.
• A valley is a sequence of consecutive steps below sea level, starting with a step down from sea level and ending with a step up to sea level.

Given Gary's sequence of up and down steps during his last hike, find and print the number of valleys he walked through.

For example, if Gary's path is s=[DDUUUUDD] he first enters a valley 2 units deep. Then he climbs out an up onto a mountain 2 units high. Finally, he returns to sea level and ends his hike.

Input Format:
The first line contains an integer n, the number of steps in Gary's hike. 
The second line contains a single string s, of n characters that describe his path.

Constraints:
2 <= n<=10^6

Output Format:
Print a single integer that denotes the number of valleys Gary walked through during his hike.

Sample Input:
8
UDDDUDUU

Sample Output:
1

Explanation:
If we represent _ as sea level, a step up as /, and a step down as \, Gary's hike can be drawn as:

_/\      _
   \    /
    \/\/
He enters and leaves one valley.

Solution:

1. // countingValleys function below.
2.     static int countingValleys(int n, String s) {
3.         char c[] = s.toCharArray();
4.         int lvl = 0;    // level
5.         int v = 0;      // valley
6.         for(int i = 0; i <c.length; i++)
7.         {
8.             if(c[i] == 'U')
9.             {
10.                 lvl = lvl +1;
11.             }
12.             if(c[i] == 'D')
13.             { 
14.                 lvl = lvl -1;
15.             }
16.             if(lvl == 0 && c[i] == 'U')
17.             {
18.                 v = v +1;
19.             }
20.         }
21.         return v;
22.     }

How do you solve the problem of a sock merchant?

Problem statement:
John works at a clothing store. He has a large pile of socks that he must pair by color for sale. Given an array of integers representing the color of each sock, determine how many pairs of socks with matching colors there are.

For example, there are n = 7 socks with colors ar = [1,2,1,2,1,3,2] . There is one pair of color 1 and one of color 2. There are three odd socks left, one of each color. The number of pairs is 2.

Input Format:
The first line contains an integer n, the number of socks represented in ar. 

The second line contains n space-separated integers describing the colors ar[i] of the socks in the pile.

Constraints:
1 <= n <=100
1 <= ar[i] <= 100 where 0 <= i < n

Output Format:
Return the total number of matching pairs of socks that John can sell.

Sample Input:
9
10 20 20 10 10 30 50 10 20

Sample Output:
3

1. // sockMerchant function below.
2.     static int sockMerchant(int n, int[] ar) {        
3.         int count = 0;
4.         Arrays.sort(ar);
5.         for(int i = 0; i < ar.length-1; i++)
6.         {
7.             if(ar[i] == ar[i+1])
8.             {
9.                 count = count+1; // count++;
10.                 //i+=1;
11.                 i = i+1;        
12.             }
13.         }        
14.         return count;
15.     }