Reaching a point using clockwise or anticlockwise movements

• Last Updated : 06 Sep, 2021

Given starting and ending position and a number N. Given that we are allowed to move in only four directions as shown in the image below. The directions of moves are U( ), R , D and L . We need to write a program to determine if starting from the given starting position we can reach the given end position in exactly N moves in moving about any direction(Clockwise or Anticlockwise). Examples :

Input: start = U , end = L , N = 3
Output: Clockwise
Explanation: Step 1: move clockwise to reach R
Step 2: move clockwise to reach D
Step 3: move clockwise to reach L
So we reach from U to L in 3 steps moving in
clockwise direction.

Input: start = R , end = L , N = 3
Output: Not possible
Explanation: It is not possible to start from
R and end at L in 3 steps moving about in any
direction.

Input: start = D , end = R , N = 7
Output: Clockwise
Explanation: Starting at D, we complete one
complete clockwise round in 4 steps to reach D
again, then it takes 3 step to reach R

The idea to solve this problem is to observe that we can complete one round in 4 steps by traveling in any direction (clockwise or anti-clockwise), so taking n%4 steps is equivalent to taking n steps from the starting point. Therefore n is reduced to n%4. Consider the values of ‘U’ as 0, ‘R’ as 1, ‘D’ as 2 and ‘L’ as 3. If the abs(value(a)-value(b)) is 2 and n is also 2, then we can move either in clockwise or anticlockwise direction to reach the end position from the start position. If moving k steps in clockwise direction take us to the end position from start position then we can say that the condition for clockwise move will be (value(a)+k)%4==value(b). Similarly, the condition for anticlockwise move will be (value(a)+k*3)%4==value(b) since taking k step from position a in clockwise direction is equivalent to taking (a + k*3)%4 steps in anticlockwise direction.
Below is the implementation of the above approach:

C++

 // CPP program to determine if// starting from the starting// position we can reach the // end position in N moves// moving about any direction#include using namespace std; // function that returns mark// up value of directionsint value(char a){    if (a == 'U')        return 0;    if (a == 'R')        return 1;    if (a == 'D')        return 2;    if (a == 'L')        return 3;} // function to print// the possible movevoid printMove(char a, char b, int n){    // mod with 4 as completing    // 4 steps means completing    // one single round    n = n % 4;     // when n is 2 and the    // difference between moves is 2    if (n == 2 and abs(value(a) -                       value(b)) == 2)        cout << "Clockwise or Anticlockwise";     // anticlockwise condition    else if ((value(a) + n * 3) % 4 == value(b))        cout << "Anticlockwise";     // clockwise condition    else if ((value(a) + n) % 4 == value(b))        cout << "Clockwise";    else        cout << "Not Possible";} // Driver Codeint main(){    char a = 'D', b = 'R';    int n = 7;    printMove(a, b, n);     return 0;}

Java

 // Java program to determine if// starting from the starting// position we can reach the// end position in N moves// moving about any directionclass GFG{    // function that returns mark    // up value of directions    static int value(char a)    {        if (a == 'U')            return 0;        if (a == 'R')            return 1;        if (a == 'D')            return 2;        if (a == 'L')            return 3;                         return -1;    }     // function to print    // the possible move    static void printMove(char a,                          char b,                          int n)    {        // mod with 4 as completing        // 4 steps means completing        // one single round        n = n % 4;             // when n is 2 and        // the difference        // between moves is 2        if (n == 2 && Math.abs(value(a) -                               value(b)) == 2)            System.out.println("Clockwise " +                        " or Anticlockwise");             // anticlockwise condition        else if ((value(a) + n * 3) %                       4 == value(b))            System.out.println("Anticlockwise");             // clockwise condition        else if ((value(a) + n) % 4 == value(b))            System.out.println("Clockwise");        else            System.out.println("Not Possible");    }     // Driver Code    public static void main(String args[])    {        char a = 'D', b = 'R';        int n = 7;        printMove(a, b, n);    }} // This code is contributed by Sam007

Python3

 # python program to determine# if starting from the starting# position we can reach the end# position in N moves moving # any direction # function that returns mark# up value of directionsdef value(a):         if (a == 'U'):        return 0    if (a == 'R'):        return 1    if (a == 'D'):        return 2    if (a == 'L'):        return 3 # function to print# the possible movedef printMove(a, b, n):         # mod with 4 as completing    # 4 steps means completing    # one single round    n = n % 4;     # when n is 2 and    # the difference    # between moves is 2    if (n == 2 and        abs(value(a) - value(b)) == 2):        print ("Clockwise or Anticlockwise")     # anticlockwise condition    elif ((value(a) + n * 3) % 4 == value(b)):        print ("Anticlockwise")     # clockwise condition    elif ((value(a) + n) % 4 == value(b)):        print ("Clockwise")    else:        print ("Not Possible")  # Driver Codea = 'D'b = 'R'n = 7printMove(a, b, n) # This code is contributed by Sam007.

C#

 // C# program to determine// if starting from the// starting position we// can reach the end position// in N moves moving about// any directionusing System; class GFG{    // function that returns mark    // up value of directions    static int value(char a)    {        if (a == 'U')            return 0;        if (a == 'R')            return 1;        if (a == 'D')            return 2;        if (a == 'L')            return 3;                     return -1;    }     // function to print    // the possible move    static void printMove(char a,                          char b,                          int n)    {        // mod with 4 as completing        // 4 steps means completing        // one single round        n = n % 4;             // when n is 2 and        // the difference        // between moves is 2        if (n == 2 && Math.Abs(value(a) -                               value(b)) == 2)            Console.Write("Clockwise " +                    "or Anticlockwise");             // anticlockwise condition        else if ((value(a) + n * 3) %                        4 == value(b))            Console.Write("Anticlockwise");             // clockwise condition        else if ((value(a) + n) %                    4 == value(b))            Console.WriteLine("Clockwise");        else            Console.WriteLine("Not Possible");    }     // Driver Code    public static void Main()    {    char a = 'D', b = 'R';    int n = 7;    printMove(a, b, n);    }} // This code is contributed by Sam007



Javascript



Output :

Clockwise

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