# Convert a Mobile Numeric Keypad sequence to equivalent sentence

Given a string S of size N, consisting of digits [0 – 9] and character ‘.’, the task is to print the string that can be obtained by pressing the mobile keypad in the given sequence.

Note: ‘.’ represents a break while typing.

Below is the image to represent the characters associated with each number in the keypad. Examples:

Input: S = “234”
Explanation:
Pressing the keys 2, 3, and 4 once gives the resultant string as “ADG”.

Input: S = “22.22”
Output: BB
Explanation:
Pressing the key 2 twice gives B, and then again pressing the key twice gives B. Therefore, the resultant string is “BB”.

Approach: The given problem can be solved by storing the mobile keypad mappings in an array and then traverse the string S and convert it into its equivalent string. Follow the steps below to solve the problem:

• Initialize an empty string, say ans to store the required result.
• Store the string associated to each key in the mobile keypad in an array nums[] such that nums[i] represent the set of characters on pressing the digit i.
• Traverse the given string S using the variable i and perform the following steps:
• If S[i] is equal to ‘.’, then increment i by 1, and continue to the next iteration.
• Otherwise, initialize a variable cnt as 0 to store the count of the same characters.
• Iterate until S[i] is equal to S[i + 1] and in each iteration check the following conditions:
• If cnt is equal to 2 and S[i] is 2, 3, 4, 5, 6, or 8, then break out of the loop because keys: 2, 3, 4, 5, 6, and 8 contain the same number of characters, i.e., 3.
• If cnt is equal to 3 and S[i] is 7 or 9, then break out of the loop because keys: 7 and 9 contain the same number of characters, i.e., 4.
• Increment the value of cnt and i by 1.
• If S[i] is either 7 or 9, then add the character nums[str[i]][cnt%4] to the string ans.
• Otherwise, add the character nums[str[i]][cnt%3] to the string ans.
• Increment the value of i by 1.
• After completing the above steps, print the value string ans as the result.

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach` `#include ` `using` `namespace` `std;`   `// Function to convert mobile numeric` `// keypad sequence into its equivalent` `// string` `void` `printSentence(string str)` `{` `    ``// Store the mobile keypad mappings` `    ``char` `nums[]` `        ``= { ``""``, ``""``, ``"ABC"``, ``"DEF"``, ``"GHI"``,` `            ``"JKL"``, ``"MNO"``, ``"PQRS"``, ``"TUV"``,` `            ``"WXYZ"` `};`   `    ``// Traverse the string str` `    ``int` `i = 0;` `    ``while` `(str[i] != ``'\0'``) {`   `        ``// If the current character is` `        ``// '.', then continue to the` `        ``// next iteration` `        ``if` `(str[i] == ``'.'``) {` `            ``i++;` `            ``continue``;` `        ``}`   `        ``// Stores the number of` `        ``// continuous clicks` `        ``int` `count = 0;`   `        ``// Iterate a loop to find the` `        ``// count of same characters` `        ``while` `(str[i + 1]` `               ``&& str[i] == str[i + 1]) {`   `            ``// 2, 3, 4, 5, 6 and 8 keys will` `            ``// have maximum of 3 letters` `            ``if` `(count == 2` `                ``&& ((str[i] >= ``'2'` `                     ``&& str[i] <= ``'6'``)` `                    ``|| (str[i] == ``'8'``)))` `                ``break``;`   `            ``// 7 and 9 keys will have` `            ``// maximum of 4 keys` `            ``else` `if` `(count == 3` `                     ``&& (str[i] == ``'7'` `                         ``|| str[i] == ``'9'``))` `                ``break``;` `            ``count++;` `            ``i++;`   `            ``// Handle the end condition` `            ``if` `(str[i] == ``'\0'``)` `                ``break``;` `        ``}`   `        ``// Check if the current pressed` `        ``// key is 7 or 9` `        ``if` `(str[i] == ``'7'` `|| str[i] == ``'9'``) {` `            ``cout << nums[str[i] - 48][count % 4];` `        ``}`   `        ``// Else, the key pressed is` `        ``// either 2, 3, 4, 5, 6 or 8` `        ``else` `{` `            ``cout << nums[str[i] - 48][count % 3];` `        ``}` `        ``i++;` `    ``}` `}`   `// Driver Code` `int` `main()` `{` `    ``string str = ``"234"``;` `    ``printSentence(str);` `    ``return` `0;` `}`

## Java

 `// java program for the above approach` `import` `java.io.*;` `import` `java.lang.*;` `import` `java.util.*;`   `public` `class` `GFG {`   `    ``// Function to convert mobile numeric` `    ``// keypad sequence into its equivalent` `    ``// string` `    ``static` `void` `printSentence(String S)` `    ``{` `        ``// Store the mobile keypad mappings` `        ``String nums[]` `            ``= { ``""``,    ``""``,    ``"ABC"``,  ``"DEF"``, ``"GHI"``,` `                ``"JKL"``, ``"MNO"``, ``"PQRS"``, ``"TUV"``, ``"WXYZ"` `};`   `        ``char` `str[] = S.toCharArray();`   `        ``// Traverse the string str` `        ``int` `i = ``0``;` `        ``while` `(i < str.length) {`   `            ``// If the current character is` `            ``// '.', then continue to the` `            ``// next iteration` `            ``if` `(str[i] == ``'.'``) {` `                ``i++;` `                ``continue``;` `            ``}`   `            ``// Stores the number of` `            ``// continuous clicks` `            ``int` `count = ``0``;`   `            ``// Iterate a loop to find the` `            ``// count of same characters` `            ``while` `(i + ``1` `< str.length` `                   ``&& str[i] == str[i + ``1``]) {`   `                ``// 2, 3, 4, 5, 6 and 8 keys will` `                ``// have maximum of 3 letters` `                ``if` `(count == ``2` `                    ``&& ((str[i] >= ``'2'` `&& str[i] <= ``'6'``)` `                        ``|| (str[i] == ``'8'``)))` `                    ``break``;`   `                ``// 7 and 9 keys will have` `                ``// maximum of 4 keys` `                ``else` `if` `(count == ``3` `                         ``&& (str[i] == ``'7'` `                             ``|| str[i] == ``'9'``))` `                    ``break``;` `                ``count++;` `                ``i++;`   `                ``// Handle the end condition` `                ``if` `(i == str.length)` `                    ``break``;` `            ``}`   `            ``// Check if the current pressed` `            ``// key is 7 or 9` `            ``if` `(str[i] == ``'7'` `|| str[i] == ``'9'``) {` `                ``System.out.print(` `                    ``nums[str[i] - ``48``].charAt(count % ``4``));` `            ``}`   `            ``// Else, the key pressed is` `            ``// either 2, 3, 4, 5, 6 or 8` `            ``else` `{` `                ``System.out.print(` `                    ``nums[str[i] - ``48``].charAt(count % ``3``));` `            ``}` `            ``i++;` `        ``}` `    ``}`   `    ``// Driver Code` `    ``public` `static` `void` `main(String[] args)` `    ``{`   `        ``String str = ``"234"``;` `        ``printSentence(str);` `    ``}` `}`   `// This code is contributed by Kingash.`

## Python3

 `# Python3 program for the above approach`   `# Function to convert mobile numeric` `# keypad sequence into its equivalent` `# string` `def` `printSentence(str1):` `    `  `    ``# Store the mobile keypad mappings` `    ``nums ``=` `[ "``", "``", "``ABC``", "``DEF``", "``GHI``", "``JKL",` `             ``"MNO"``, ``"PQRS"``, ``"TUV"``, ``"WXYZ"` `]`   `    ``# Traverse the string str1` `    ``i ``=` `0` `    `  `    ``while` `(i < ``len``(str1)):` `        `  `        ``# If the current character is` `        ``# '.', then continue to the` `        ``# next iteration` `        ``if` `(str1[i] ``=``=` `'.'``):` `            ``i ``+``=` `1` `            ``continue`   `        ``# Stores the number of` `        ``# continuous clicks` `        ``count ``=` `0`   `        ``# Iterate a loop to find the` `        ``# count of same characters` `        ``while` `(i ``+` `1` `< ``len``(str1) ``and` `str1[i ``+` `1``] ``and` `                          ``str1[i] ``=``=` `str1[i ``+` `1``]):`   `            ``# 2, 3, 4, 5, 6 and 8 keys will` `            ``# have maximum of 3 letters` `            ``if` `(count ``=``=` `2` `and` `((str1[i] >``=` `'2'` `and` `             ``str1[i] <``=` `'6'``) ``or` `(str1[i] ``=``=` `'8'``))):` `                ``break`   `            ``# 7 and 9 keys will have` `            ``# maximum of 4 keys` `            ``elif` `(count ``=``=` `3` `and` `(str1[i] ``=``=` `'7'` `or` `                                  ``str1[i] ``=``=` `'9'``)):` `                ``break` `            `  `            ``count ``+``=` `1` `            ``i ``+``=` `1`   `            ``# Handle the end condition` `            ``if` `(i < ``len``(``str``)):` `                ``break`   `        ``# Check if the current pressed` `        ``# key is 7 or 9` `        ``if` `(str1[i] ``=``=` `'7'` `or` `str1[i] ``=``=` `'9'``):` `            ``print``(nums[``ord``(str1[i]) ``-` `48``][count ``%` `4``], end ``=` `"")`   `        ``# Else, the key pressed is` `        ``# either 2, 3, 4, 5, 6 or 8` `        ``else``:` `            ``print``(nums[``ord``(str1[i]) ``-` `48``][count ``%` `3``], end ``=` `"")` `            `  `        ``i ``+``=` `1`   `# Driver Code` `if` `__name__ ``=``=` `'__main__'``:` `    `  `    ``str1 ``=` `"234"` `    ``printSentence(str1)`   `# This code is contributed by bgangwar59`

## C#

 `// C# program for the above approach` `using` `System;` `public` `class` `GFG` `{`   `    ``// Function to convert mobile numeric` `    ``// keypad sequence into its equivalent` `    ``// string` `    ``static` `void` `printSentence(``string` `S)` `    ``{` `      `  `        ``// Store the mobile keypad mappings` `        ``string``[] nums` `            ``= { ``""``,    ``""``,    ``"ABC"``,  ``"DEF"``, ``"GHI"``,` `                ``"JKL"``, ``"MNO"``, ``"PQRS"``, ``"TUV"``, ``"WXYZ"` `};`   `        ``char``[] str = S.ToCharArray();`   `        ``// Traverse the string str` `        ``int` `i = 0;` `        ``while` `(i < str.Length) {`   `            ``// If the current character is` `            ``// '.', then continue to the` `            ``// next iteration` `            ``if` `(str[i] == ``'.'``) {` `                ``i++;` `                ``continue``;` `            ``}`   `            ``// Stores the number of` `            ``// continuous clicks` `            ``int` `count = 0;`   `            ``// Iterate a loop to find the` `            ``// count of same characters` `            ``while` `(i + 1 < str.Length` `                   ``&& str[i] == str[i + 1]) {`   `                ``// 2, 3, 4, 5, 6 and 8 keys will` `                ``// have maximum of 3 letters` `                ``if` `(count == 2` `                    ``&& ((str[i] >= ``'2'` `&& str[i] <= ``'6'``)` `                        ``|| (str[i] == ``'8'``)))` `                    ``break``;`   `                ``// 7 and 9 keys will have` `                ``// maximum of 4 keys` `                ``else` `if` `(count == 3` `                         ``&& (str[i] == ``'7'` `                             ``|| str[i] == ``'9'``))` `                    ``break``;` `                ``count++;` `                ``i++;`   `                ``// Handle the end condition` `                ``if` `(i == str.Length)` `                    ``break``;` `            ``}`   `            ``// Check if the current pressed` `            ``// key is 7 or 9` `            ``if` `(str[i] == ``'7'` `|| str[i] == ``'9'``) {` `                ``Console.Write(nums[str[i] - 48][count % 4]);` `            ``}`   `            ``// Else, the key pressed is` `            ``// either 2, 3, 4, 5, 6 or 8` `            ``else` `{` `                ``Console.Write(nums[str[i] - 48][count % 3]);` `            ``}` `            ``i++;` `        ``}` `    ``}`   `    ``// Driver Code` `    ``public` `static` `void` `Main(``string``[] args)` `    ``{`   `        ``string` `str = ``"234"``;` `        ``printSentence(str);` `    ``}` `}`   `// This code is contributed by ukasp.`

## Javascript

 ``

Output:

`ADG`

Time Complexity: O(N)
Auxiliary Space: O(1)

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