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Total time required to travel a path denoted by a given string

  • Last Updated : 28 Jun, 2021
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Given a string path consisting of characters ‘N’, ‘S’, ‘E’ and ‘W’ denoting 1 unit movement in North, South, East, and West directions respectively, the task is to find the time taken to travel the complete path starting from the origin, if it takes 2 and 1 minutes to travel on an unvisited and visited segment respectively.

Examples :

Input: path = “NNES”
Output : 8

Explanation: Since every segment is visited only once, cost = 2 * 4 = 8.



Input : path = “NSE”
Output : 5

Explanation: 
Step 1: Travel north. Time Taken = 2 minutes. 
Step 2: Travel south on that same visited segment. Time Taken = 1 minutes. 
Step 3: Travel east.Time Taken = 2 minutes. Therefore, total time taken = 2 + 1 + 2 = 5.

Approach: The idea is to use a Set to store all the visited segments and before visiting each segment, check if it is present in the Set or not. Follow the steps below to solve the problem.

  • Initialize a set s to store a pair of integers. The set will store all visited segments.
  • Initialize two integers x = 0 and y = 0 denoting the current position. Also, initialize a variable time = 0 to store the total time needed to travel the complete path.
  • Traverse the string and follow the below steps
    • Initialize two integers p and q to x and y respectively.
    • If path[i] is equal to ‘N’ increment y, else if path[i] is equal to ‘S’ decrement y, else if path[i] is equal to ‘E’ increment x, otherwise decrement x.
    • Check if the segment {p+x, q+y} exists in the set or not. if it does add 1 to the value of time otherwise add 2 to the value of time.
    • Insert the segment {p+x, q+y} into the set.
  • After completing the above steps print the value of time.

Below is implementation of the above approach.

C++




// C++ code for the above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to calculate time
// taken to travel the path
void calcTotalTime(string path)
{
    // Stores total time
    int time = 0;
 
    // Initial position
    int x = 0, y = 0;
 
    // Stores visited segments
    set<pair<int, int> > s;
 
    for (int i = 0; i < path.size(); i++) {
 
        int p = x;
        int q = y;
 
        if (path[i] == 'N')
            y++;
 
        else if (path[i] == 'S')
            y--;
 
        else if (path[i] == 'E')
            x++;
 
        else if (path[i] == 'W')
            x--;
 
        // Check whether segment
        // is present in the set
        if (s.find({ p + x, q + y })
            == s.end()) {
            // Increment the value
            // of time by 2
            time += 2;
 
            // Insert segment into the set
            s.insert({ p + x, q + y });
        }
        else
            time += 1;
    }
 
    // Print the value
    // of time
    cout << time << endl;
}
 
// Driver Code
int main()
{
    string path = "NSE";
 
    calcTotalTime(path);
 
    return 0;
}

Java




// Java program for above approach
import java.util.*;
 
class GFG{
 
// Function to calculate time
// taken to travel the path
static void calcTotalTime(String path)
{
     
    // Stores total time
    int time = 0;
 
    // Initial position
    int x = 0, y = 0;
 
    // Stores visited segments
    Set<String> s = new HashSet<>();
    for(int i = 0; i < path.length(); i++)
    {
        int p = x;
        int q = y;
 
        if (path.charAt(i) == 'N')
            y++;
 
        else if (path.charAt(i) == 'S')
            y--;
 
        else if (path.charAt(i) == 'E')
            x++;
 
        else if (path.charAt(i) == 'W')
            x--;
 
        // Check whether segment
        // is present in the set
        String o = (p + x) + " " + (q + y);
        if (!s.contains(o))
        {
             
            // Increment the value
            // of time by 2
            time += 2;
 
            // Insert segment into the set
            s.add(o);
        }
        else
            time += 1;
    }
 
    // Print the value
    // of time
    System.out.println(time);
}
 
// Driver Code
public static void main(String[] args)
{
    String path = "NSE";
 
    calcTotalTime(path);
}
}
 
// This code is contributed by Hritik

Python3




# Python 3 code for the above approach
 
# Function to calculate time
# taken to travel the path
def calcTotalTime(path):
 
    # Stores total time
    time = 0
 
    # Initial position
    x = 0
    y = 0
 
    # Stores visited segments
    s = set([])
 
    for i in range(len(path)):
 
        p = x
        q = y
 
        if (path[i] == 'N'):
            y += 1
 
        elif (path[i] == 'S'):
            y -= 1
 
        elif (path[i] == 'E'):
            x += 1
 
        elif (path[i] == 'W'):
            x -= 1
 
        # Check whether segment
        # is present in the set
        if (p + x, q + y) not in s:
            # Increment the value
            # of time by 2
            time += 2
 
            # Insert segment into the set
            s.add((p + x, q + y))
 
        else:
            time += 1
 
    # Print the value
    # of time
    print(time)
 
 
# Driver Code
if __name__ == "__main__":
 
    path = "NSE"
 
    calcTotalTime(path)
 
    # This code is contributed by ukasp.

C#




// C# program for the above approach
using System;
using System.Collections.Generic;
 
class GFG{
 
// Function to calculate time
// taken to travel the path
static void calcTotalTime(string path)
{
     
    // Stores total time
    int time = 0;
 
    // Initial position
    int x = 0, y = 0;
 
    // Stores visited segments
    HashSet<string> s = new HashSet<string>();
    for(int i = 0; i < path.Length; i++)
    {
        int p = x;
        int q = y;
 
        if (path[i] == 'N')
            y++;
 
        else if (path[i] == 'S')
            y--;
 
        else if (path[i] == 'E')
            x++;
 
        else if (path[i] == 'W')
            x--;
 
        // Check whether segment
        // is present in the set
        string o = (p + x) + " " + (q + y);
        if (s.Contains(o) == false)
        {
             
            // Increment the value
            // of time by 2
            time += 2;
 
            // Insert segment into the set
            s.Add(o);
        }
        else
            time += 1;
    }
 
    // Print the value
    // of time
    Console.Write(time);
}
 
// Driver Code
public static void Main()
{
    string path = "NSE";
 
    calcTotalTime(path);
}
}
 
// This code is contributed by bgangwar59

Javascript




<script>
 
// Javascript code for the above approach
 
// Function to calculate time
// taken to travel the path
function calcTotalTime(path)
{
     
    // Stores total time
    var time = 0;
 
    // Initial position
    var x = 0, y = 0;
 
    // Stores visited segments
    var s = new Set();
 
    for(var i = 0; i < path.length; i++)
    {
        var p = x;
        var q = y;
 
        if (path[i] == 'N')
            y++;
 
        else if (path[i] == 'S')
            y--;
 
        else if (path[i] == 'E')
            x++;
 
        else if (path[i] == 'W')
            x--;
 
        // Check whether segment
        // is present in the set
        if (!s.has([p + x, q + y].toString()))
        {
             
            // Increment the value
            // of time by 2
            time += 2;
 
            // Insert segment into the set
            s.add([p + x, q + y].toString());
        }
        else
            time += 1;
    }
 
    // Print the value
    // of time
    document.write(time)
}
 
// Driver Code
var path = "NSE";
 
calcTotalTime(path);
 
</script>
Output: 
5

 

Time Complexity: O(NlogN)
Auxiliary Space: O(N)

 

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