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Count of buttons pressed in a keypad mobile

  • Difficulty Level : Medium
  • Last Updated : 26 Mar, 2021

Given a string str, the task is to count how many times the keys will be pressed in total if there is a mobile like below image to form the given string. 
 

Examples: 
 

Input: str = “abcdef” 
Output: 12 
1 for a, 2 for b, 3 for c, 1 for d, 2 for e and 3 for f 
Total = 1 + 2 + 3 + 1 + 2 + 3 = 12
Input: str = “ssss” 
Output: 16 
 

 



Approach: Use an array to store how many times a button has to be pressed for typing a particular character and then traverse the given string character by character and add all the corresponding count of key presses to the sum variable.
Below is the implementation of the above approach:
 

C++




// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
// Array to store how many times a button
// has to be pressed for typing
// a particular character
const int arr[] = { 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1,
                    2, 3, 1, 2, 3, 4, 1, 2, 3, 1, 2, 3, 4 };
 
// Function to return the count of
// buttons pressed to type the given string
int countKeyPressed(string str, int len)
{
    int count = 0;
 
    // Count the key presses
    for (int i = 0; i < len; i++)
        count = count + arr[str[i] - 'a'];
 
    // Return the required count
    return count;
}
 
// Driver code
int main()
{
    string str = "abcdef";
    int len = str.length();
    cout << countKeyPressed(str, len);
 
    return 0;
}

Java




// Java implementation of the approach
class GFG {
 
    // Array to store how many times a button
    // has to be pressed for typing
    // a particular character
    static final int arr[] = { 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1,
                               2, 3, 1, 2, 3, 4, 1, 2, 3, 1, 2, 3, 4 };
 
    // Function to return the count of
    // buttons pressed to type the given string
    public static int countKeyPressed(String str, int len)
    {
        int count = 0;
 
        // Count the key presses
        for (int i = 0; i < len; i++)
            count = count + arr[str.charAt(i) - 'a'];
 
        // Return the required count
        return count;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String str = "abcdef";
        int len = str.length();
        System.out.print(countKeyPressed(str, len));
    }
}

Python3




# Python3 implementation of the approach
 
# Array to store how many times a button
# has to be pressed for typing
# a particular character
arr = [ 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1,
        2, 3, 1, 2, 3, 4, 1, 2, 3, 1, 2, 3, 4 ];
 
# Function to return the count of
# buttons pressed to type the given string
def countKeyPressed(string, length) :
    count = 0;
 
    # Count the key presses
    for i in range(length) :
        count += arr[ord(string[i]) - ord('a')];
 
    # Return the required count
    return count;
 
# Driver code
if __name__ == "__main__" :
    string = "abcdef";
    length = len(string);
     
    print(countKeyPressed(string, length));
 
# This code is contributed by Ryuga

C#




// C# implementation of the approach
using System;
class GFG {
 
    // Array to store how many times a button
    // has to be pressed for typing
    // a particular character
    static readonly int[] arr = { 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1,
                                  2, 3, 1, 2, 3, 4, 1, 2, 3, 1, 2, 3, 4 };
 
    // Function to return the count of
    // buttons pressed to type the given string
    public static int countKeyPressed(String str, int len)
    {
        int count = 0;
 
        // Count the key presses
        for (int i = 0; i < len; i++)
            count = count + arr[str[i] - 'a'];
 
        // Return the required count
        return count;
    }
 
    // Driver code
    public static void Main()
    {
        String str = "abcdef";
        int len = str.Length;
        Console.Write(countKeyPressed(str, len));
    }
}

PHP




<?php
// PHP implementation of the approach
 
// Array to store how many times a
// button has to be pressed for
// typing a particular character
$arr = array( 1, 2, 3, 1, 2, 3,
              1, 2, 3, 1, 2, 3, 1,
              2, 3, 1, 2, 3, 4, 1,
              2, 3, 1, 2, 3, 4 );
 
// Function to return the count of
// buttons pressed to type the given string
function countKeyPressed($str, $len)
{
    global $arr;
    $count = 0;
 
    // Count the key presses
    for ($i = 0; $i < $len; $i++)
        $count = $count + $arr[ord($str[$i]) -
                               ord('a')];
 
    // Return the required count
    return $count;
}
 
// Driver code
$str = "abcdef";
$len = strlen($str);
echo countKeyPressed($str, $len);
 
// This code is contributed by ita_c
?>

Javascript




<script>
 
 
// Javascript implementation of the approach
 
// Array to store how many times a button
// has to be pressed for typing
// a particular character
var arr = [ 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1,
                    2, 3, 1, 2, 3, 4, 1, 2, 3, 1, 2, 3, 4 ]
 
// Function to return the count of
// buttons pressed to type the given string
function countKeyPressed(str, len)
{
    var count = 0;
 
    // Count the key presses
    for (var i = 0; i < len; i++)
        count = count + arr[str.charCodeAt(i) - 97];
 
    // Return the required count
    return count;
}
 
// Driver code
var str = "abcdef";
var len = str.length;
document.write(countKeyPressed(str, len));
 
// This code is contributed by noob2000.
</script>
Output: 
12

 

Time Complexity: O(n)
 

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