Passing the Assignment

Rachel is submitting assignment from every student. She has given them a few minutes to arrange their assignments before submission. Just then Rahul remembers that his assignment is with Rohan. Rohan has to pass the assignment to Rahul. All the students are sitting in a straight line. He cannot pass the assignment in front of the teacher because then she will assume they have copied the assignment and will punish both of them. We have to help Rohan to find a way to pass the assignment to Rahul in such a way that he is not caught.
Assignment can be passed under some restrictions as given below:

• A student can pass the assignment only to his immediate neighbor i.e i-1 and i+1
• At any given time a student may pass the assignment to other student, accept the assignment from some other student or may keep the assignment to himself.
• Teacher is keeping watch over students from to including both and • If a student is being watched he cannot pass the note or accept the note, otherwise he is caught.
• If he keeps the assignment and he is being watched, he is not caught.

Given four inputs n, m, s, f where n is the total number of students, m is the number of steps during which teacher keeps vigil over students from to , s is the position of Rohan and f is the position of Rahul.
Each m query contains three inputs: The time at which she is watching, the leftmost child she is watching and the rightmost child she is watching.
We have to output a sequence of three words:  and denoting the passing direction of current student.

Examples:

Input: n = 4, m = 4, s = 3, f = 4
1 2 4
2 1 2
3 3 4
4 2 3
Output: KeepRight
During time = 1, teacher is watching all
the student from 2 to 4. Student 3 who
has the assignment therefore cannot pass
it to his neighbor, thus he keeps the
assignment. During time = 2, teacher is
watching student 1 and 2, therefore
student 3 can pass the assignment to
his right to student 4. Since student
4 is Rahul therefore our answer is
"KeepRight"

Input: n = 10, m = 1, s = 1, f = 10
1 5 6
Output: RightRightRightRightRightRight
RightRightRightRight
During time = 1, teacher is watching
student 5 and 6 therefore student 1
can easily pass the assignment to his
right to student 2. After this teacher
stops watching any student therefore
they can keep on passing the assignment
to their right until the assignment
reaches Rahul. Therefore the answer is
"RightRightRightRightRightRight
RightRightRightRight"

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach:
At a given moment if the teacher is watching either the student currently holding the assignment or the student to whom the assignment is to be passed, then the student will keep it to himself else he will pass the assignment to his neighbor sitting towards Rahul.

Below is the implementation:

C++

 // CPP program to find the way #include using namespace std;    void solve(int n, int m, int s, int f,         long t[], int l[], int r[]) {        int dir;     string val;        // If Rahul sits to right of Rohan     // then student will either pass     // it right or keep it to himself     if (s < f) {         dir = 1;         val = "Right";     }        // If Rahul sits to left of Rohan     // then student will either pass     // it left or keep it to himself     else {         dir = -1;         val = "Left";     }     string ans = "";        // current is keeping track of     // the position of assignment     // at a given time     int i = 0, current = s;        // tim variable keeping track of     // current time     long tim = 1;     while (1) {            // If time duration of query         // matches with the current time         if (i < m && tim == t[i]) {                // If teacher is watching the             // student having the assignment             // or the student to whom the             // assignment is to be passed             // then the student keeps it to             // itself             if ((current >= l[i] && current <= r[i]) ||                 (current + dir >= l[i] && current + dir                                           <= r[i])) {                 ans += "Keep";                 tim++;                 i++;                 continue;             }             i++;         }            // If the students are safe then student         // passes the assignment to his neighbor         current += dir;         ans += val;         tim++;            // If the assignment has reached Rahul         // then we break the loop         if (current == f)             break;     }        cout << ans << endl; }    // Driver function for the program int main() {     int n = 4, m = 4, s = 3, f = 4;        // matrix saving time for each query     long t[m + 2] = { 1, 2, 3, 4 };        // matrix saving leftmost child being     // watched for each query     int l[m + 2] = { 2, 1, 3, 2 };        // matrix saving rightmost child     // being watched for each query     int r[m + 2] = { 4, 2, 4, 3 };        solve(n, m, s, f, t, l, r);     return 0; }

Java

 // Java progam to find the way import java.io.*;    class Hiding {     static void solve(int n, int m, int s, int f,                     long t[], int l[], int r[])     {         int dir;         String val;            // If Rahul sits to right of Rohan         // then student will either pass it         // right or keep it to himself         if (s < f) {             dir = 1;             val = "Right";         }            // If Rahul sits to left of Rohan then         // student will either pass it left         // or keep it to himself         else {             dir = -1;             val = "Left";         }            String ans = "";         int i = 0, current = s;            // Variable keeping track of current time         long tim = 1;         while (1 > 0) {                            // If time duration of query             // matches with the current time             if (i < m && tim == t[i]) {                                // If teacher is watching the student                 // having the assignment or the                 // student to whom the assignment is                 // to be passed then the student                 // keeps it to itself                 if ((current >= l[i] && current <= r[i]) ||                     (current + dir >= l[i] && current + dir                                                <= r[i])) {                     ans += "Keep";                     tim++;                     i++;                     continue;                 }                 i++;             }                // If the students are safe then student             // passes the assignment to his neighbor             current += dir;             ans += val;             tim++;                // If the assignment has reached Rahul             // then we break the loop             if (current == f)                 break;         }         System.out.println(ans);     }        // Driver Program     public static void main(String args[])     {         int n = 4, m = 4, s = 3, f = 4;            // matrix saving time for each query         long t[] = { 1, 2, 3, 4 };            // matrix saving leftmost child          // being watched         int l[] = { 2, 1, 3, 2 };            // matrix saving rightmost child          // being watched         int r[] = { 4, 2, 4, 3 };            solve(n, m, s, f, t, l, r);     } }

C#

 // C# progam to find the way using System;    class Hiding {     static void solve(int n, int m, int s, int f,                       long []t, int []l, int []r)     {         int dir;         String val;            // If Rahul sits to right of Rohan         // then student will either pass it         // right or keep it to himself         if (s < f) {             dir = 1;             val = "Right";         }            // If Rahul sits to left of Rohan then         // student will either pass it left         // or keep it to himself         else {             dir = -1;             val = "Left";         }            String ans = "";         int i = 0, current = s;            // Variable keeping track of current time         long tim = 1;         while (1 > 0) {                            // If time duration of query             // matches with the current time             if (i < m && tim == t[i]) {                                // If teacher is watching the student                 // having the assignment or the                 // student to whom the assignment is                 // to be passed then the student                 // keeps it to itself                 if ((current >= l[i] && current <= r[i]) ||                      (current + dir >= l[i] && current +                                           dir <= r[i]))                  {                     ans += "Keep";                     tim++;                     i++;                     continue;                 }                 i++;             }                // If the students are safe then student             // passes the assignment to his neighbor             current += dir;             ans += val;             tim++;                // If the assignment has reached Rahul             // then we break the loop             if (current == f)                 break;         }         Console.Write(ans);     }        // Driver Program     public static void Main()     {         int n = 4, m = 4, s = 3, f = 4;            // matrix saving time for each query         long []t = { 1, 2, 3, 4 };            // matrix saving leftmost          // child being watched         int []l = { 2, 1, 3, 2 };            // matrix saving rightmost         // child being watched         int []r = { 4, 2, 4, 3 };            solve(n, m, s, f, t, l, r);     } }    // This code is contributed by nitin mittal

Output:

KeepRight

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Improved By : nitin mittal

Article Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.