Find all strings formed from characters mapped to digits of a number
Last Updated :
08 Mar, 2023
Consider below list where each digit from 1 to 9 maps to few characters.
1 -> ['A', 'B', 'C']
2 -> ['D', 'E', 'F']
3 -> ['G', 'H', 'I']
4 -> ['J', 'K', 'L']
5 -> ['M', 'N', 'O']
6 -> ['P', 'Q', 'R']
7 -> ['S', 'T', 'U']
8 -> ['V', 'W', 'X']
9 -> ['Y', 'Z']
Given a number, replace its digits with corresponding characters in given list and print all strings possible. Same character should be considered for every occurrence of a digit in the number. Input number is positive and doesn't contain 0. Examples :
Input : 121
Output : ADA BDB CDC AEA BEB CEC AFA BFB CFC
Input : 22
Output : DD EE FF
The idea is for each digit in the input number, we consider strings formed by the previous digit and append characters mapped to the current digit to them. If this is not the first occurrence of the digit, we append the same character as used in its first occurrence.
Implementation:
C++
// C++ program to find all strings formed from a given
// number where each digit maps to given characters.
#include <bits/stdc++.h>
using namespace std;
// Function to find all strings formed from a given
// number where each digit maps to given characters.
vector<string> findCombinations(vector<int> input,
vector<char> table[])
{
// vector of strings to store output
vector<string> out, temp;
// stores index of first occurrence
// of the digits in input
unordered_map<int, int> mp;
// maintains index of current digit considered
int index = 0;
// for each digit
for (int d: input)
{
// store index of first occurrence
// of the digit in the map
if (mp.find(d) == mp.end())
mp[d] = index;
// clear vector contents for future use
temp.clear();
// do for each character that maps to the digit
for (int i = 0; i < table[d - 1].size(); i++)
{
// for first digit, simply push all its
// mapped characters in the output list
if (index == 0)
{
string s(1, table[d - 1].at(i));
out.push_back(s);
}
// from second digit onwards
if (index > 0)
{
// for each string in output list
// append current character to it.
for(string str: out)
{
// convert current character to string
string s(1, table[d - 1].at(i));
// Imp - If this is not the first occurrence
// of the digit, use same character as used
// in its first occurrence
if(mp[d] != index)
s = str[mp[d]];
str = str + s;
// store strings formed by current digit
temp.push_back(str);
}
// nothing more needed to be done if this
// is not the first occurrence of the digit
if(mp[d] != index)
break;
}
}
// replace contents of output list with temp list
if(index > 0)
out = temp;
index++;
}
return out;
}
// Driver program
int main()
{
// vector to store the mappings
vector<char> table[] =
{
{ 'A', 'B', 'C' },
{ 'D', 'E', 'F' },
{ 'G', 'H', 'I' },
{ 'J', 'K', 'L' },
{ 'M', 'N', 'O' },
{ 'P', 'Q', 'R' },
{ 'S', 'T', 'U' },
{ 'V', 'W', 'X' },
{ 'Y', 'Z' }
};
// vector to store input number
vector<int> input = { 1, 2, 1};
vector<string> out = findCombinations(input, table);
// print all possible strings
for (string it: out)
cout << it << " ";
return 0;
}
// Java Program for the above approach
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Main {
// Function to find all strings formed from a given
// number where each digit maps to given characters.
public static List<String> findCombinations(List<Integer> input,
List<Character>[] table) {
// list of strings to store output
List<String> out = new ArrayList<>();
List<String> temp = new ArrayList<>();
// stores index of first occurrence
// of the digits in input
Map<Integer, Integer> mp = new HashMap<>();
// maintains index of current digit considered
int index = 0;
// for each digit
for (int d : input) {
// store index of first occurrence
// of the digit in the map
if (!mp.containsKey(d))
mp.put(d, index);
// clear list contents for future use
temp.clear();
// do for each character that maps to the digit
for (int i = 0; i < table[d - 1].size(); i++) {
// for first digit, simply add all its
// mapped characters in the output list
if (index == 0) {
out.add(Character.toString(table[d - 1].get(i)));
}
// from second digit onwards
if (index > 0) {
// for each string in output list
// append current character to it.
for (String str : out) {
// convert current character to string
String s = Character.toString(table[d - 1].get(i));
// Imp - If this is not the first occurrence
// of the digit, use same character as used
// in its first occurrence
if (mp.get(d) != index)
s = Character.toString(str.charAt(mp.get(d)));
str = str + s;
// store strings formed by current digit
temp.add(str);
}
// nothing more needed to be done if this
// is not the first occurrence of the digit
if (mp.get(d) != index)
break;
}
}
// replace contents of output list with temp list
if (index > 0)
out = new ArrayList<>(temp);
index++;
}
return out;
}
// Driver program
public static void main(String[] args) {
// list to store the mappings
List<Character>[] table = new ArrayList[] {
new ArrayList<>(List.of('A', 'B', 'C')),
new ArrayList<>(List.of('D', 'E', 'F')),
new ArrayList<>(List.of('G', 'H', 'I')),
new ArrayList<>(List.of('J', 'K', 'L')),
new ArrayList<>(List.of('M', 'N', 'O')),
new ArrayList<>(List.of('P', 'Q', 'R')),
new ArrayList<>(List.of('S', 'T', 'U')),
new ArrayList<>(List.of('V', 'W', 'X')),
new ArrayList<>(List.of('Y', 'Z'))
};
// list to store input number
List<Integer> input = List.of(1, 2, 1);
List<String> out = findCombinations(input, table);
// print all possible strings
for (String str : out)
System.out.print(str + " ");
}
}
// This code is contributed by adityasharmadev01
# Python program to find all strings formed from a given
# number where each digit maps to given characters.
# Function to find all strings formed from a given
# number where each digit maps to given characters.
def findCombinations(input: list, table: list) -> list:
# vector of strings to store output
out, temp = [], []
# stores index of first occurrence
# of the digits in input
mp = dict()
# maintains index of current digit considered
index = 0
# for each digit
for d in input:
# store index of first occurrence
# of the digit in the map
if d not in mp:
mp[d] = index
# clear vector contents for future use
temp.clear()
# do for each character that maps to the digit
for i in range(len(table[d - 1])):
# for first digit, simply push all its
# mapped characters in the output list
if index == 0:
s = table[d - 1][i]
out.append(s)
# from second digit onwards
if index > 0:
# for each string in output list
# append current character to it.
for string in out:
# convert current character to string
s = table[d - 1][i]
# Imp - If this is not the first occurrence
# of the digit, use same character as used
# in its first occurrence
if mp[d] != index:
s = string[mp[d]]
string = string + s
# store strings formed by current digit
temp.append(string)
# nothing more needed to be done if this
# is not the first occurrence of the digit
if mp[d] != index:
break
# replace contents of output list with temp list
if index > 0:
out = temp.copy()
index += 1
return out
# Driver Code
if __name__ == "__main__":
# vector to store the mappings
table = [['A', 'B', 'C'],
['D', 'E', 'F'],
['G', 'H', 'I'],
['J', 'K', 'L'],
['M', 'N', 'O'],
['P', 'Q', 'R'],
['S', 'T', 'U'],
['V', 'W', 'X'],
['Y', 'Z']]
# vector to store input number
input = [1, 2, 1]
out = findCombinations(input, table)
# print all possible strings
for it in out:
print(it, end=" ")
# This code is contributed by
# sanjeev2552
using System;
using System.Collections.Generic;
class Program
{
// Function to find all strings formed from a given
// number where each digit maps to given characters.
static List<string> findCombinations(List<int> input, List<char>[] table)
{
// list of strings to store output
List<string> outList = new List<string>();
List<string> tempList;
// stores index of first occurrence
// of the digits in input
Dictionary<int, int> mp = new Dictionary<int, int>();
// maintains index of current digit considered
int index = 0;
// for each digit
foreach (int d in input)
{
// store index of first occurrence
// of the digit in the map
if (!mp.ContainsKey(d))
{
mp[d] = index;
}
// clear list contents for future use
tempList = new List<string>();
// do for each character that maps to the digit
for (int i = 0; i < table[d - 1].Count; i++)
{
// for first digit, simply add all its
// mapped characters in the output list
if (index == 0)
{
string s = table[d - 1][i].ToString();
outList.Add(s);
}
// from second digit onwards
if (index > 0)
{
// for each string in output list
// append current character to it.
foreach (string str in outList)
{
// convert current character to string
string s = table[d - 1][i].ToString();
// Imp - If this is not the first occurrence
// of the digit, use same character as used
// in its first occurrence
if (mp[d] != index)
{
s = str[mp[d]].ToString();
}
// store strings formed by current digit
string newStr = str + s;
tempList.Add(newStr);
}
// nothing more needed to be done if this
// is not the first occurrence of the digit
if (mp[d] != index)
{
break;
}
}
}
// replace contents of output list with temp list
if (index > 0)
{
outList = tempList;
}
index++;
}
return outList;
}
// Driver program
static void Main()
{
// list to store the mappings
List<char>[] table =
{
new List<char>{ 'A', 'B', 'C' },
new List<char>{ 'D', 'E', 'F' },
new List<char>{ 'G', 'H', 'I' },
new List<char>{ 'J', 'K', 'L' },
new List<char>{ 'M', 'N', 'O' },
new List<char>{ 'P', 'Q', 'R' },
new List<char>{ 'S', 'T', 'U' },
new List<char>{ 'V', 'W', 'X' },
new List<char>{ 'Y', 'Z' }
};
// list to store input number
List<int> input = new List<int> { 1, 2, 1 };
List<string> outList = findCombinations(input, table);
// print all possible strings
foreach (string s in outList)
{
Console.Write(s + " ");
}
}
}
<script>
// JavaScript program to find all strings formed from a given
// number where each digit maps to given characters.
// Function to find all strings formed from a given
// number where each digit maps to given characters.
function findCombinations(input,table)
{
// vector of strings to store output
let out = [], temp = [];
// stores index of first occurrence
// of the digits in input
let mp = new Map();
// maintains index of current digit considered
let index = 0;
// for each digit
for (let d of input)
{
// store index of first occurrence
// of the digit in the map
if (mp.has(d) == false)
mp.set(d , index);
// clear vector contents for future use
temp = [];
// do for each character that maps to the digit
for (let i = 0; i < table[d - 1].length; i++)
{
// for first digit, simply push all its
// mapped characters in the output list
if (index == 0)
{
let s = table[d - 1][i];
out.push(s);
}
// from second digit onwards
if (index > 0)
{
// for each string in output list
// append current character to it.
for(let str of out)
{
// convert current character to string
let s = table[d - 1][i];
// Imp - If this is not the first occurrence
// of the digit, use same character as used
// in its first occurrence
if(mp.get(d) != index)
s = str[mp.get(d)];
str = str + s;
// store strings formed by current digit
temp.push(str);
}
// nothing more needed to be done if this
// is not the first occurrence of the digit
if(mp.get(d) != index)
break;
}
}
// replace contents of output list with temp list
if(index > 0)
out = temp;
index++;
}
return out;
}
// Driver program
// vector to store the mappings
let table = [
[ 'A', 'B', 'C' ],
[ 'D', 'E', 'F' ],
[ 'G', 'H', 'I' ],
[ 'J', 'K', 'L' ],
[ 'M', 'N', 'O' ],
[ 'P', 'Q', 'R' ],
[ 'S', 'T', 'U' ],
[ 'V', 'W', 'X' ],
[ 'Y', 'Z' ]
];
// vector to store input number
let input = [ 1, 2, 1 ];
let out = findCombinations(input, table);
// print all possible strings
for (let it of out)
document.write(it , " ");
// This code is contributed by shinjanpatra
</script>
OutputADA BDB CDC AEA BEB CEC AFA BFB CFC
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