Letter Combinations of a Phone Number

shriyanshi24jindal

Mar 30th, 2026

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Java 8.56 KB | None | 0 0

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class Solution {
public List<String> letterCombinations(String digits) {
List<String> result = new ArrayList<>();
if(digits.length() == 0)
return result;
Map<Integer, String> map = new HashMap<>();
map.put(0, "");
map.put(1, "");
map.put(2, "abc");
map.put(3, "def");
map.put(4, "ghi");
map.put(5, "jkl");
map.put(6, "mno");
map.put(7, "pqrs");
map.put(8, "tuv");
map.put(9, "wxyz");
String str = "";
findCombination(digits, 0, str, result, map);
return result;
}
public void findCombination(String digits, int index, String str, List<String> result, Map<Integer, String> map)
{
if(index == digits.length())
{
result.add(str);
return;
}
char digitChar = digits.charAt(index);
int digit = digitChar - '0';
String value = map.get(digit);
for(char ch : value.toCharArray())
{
findCombination(digits, index+1, str + ch, result, map);
}
}
}
// digits = "34"
// digitChar = '3' map.get('3')="def"

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class Solution {
    public List<String> letterCombinations(String digits) {
        List<String> result = new ArrayList<>();

if(digits.length() == 0)
            return result;

Map<Integer, String> map = new HashMap<>();
        map.put(0, "");
        map.put(1, "");
        map.put(2, "abc");
        map.put(3, "def");
        map.put(4, "ghi");
        map.put(5, "jkl");
        map.put(6, "mno");
        map.put(7, "pqrs");
        map.put(8, "tuv");
        map.put(9, "wxyz");

String str = "";
        findCombination(digits, 0, str, result, map);
        return result;
    }

public void findCombination(String digits, int index, String str, List<String> result, Map<Integer, String> map)
    {
        if(index == digits.length())
        {
            result.add(str);
            return;
        }

char digitChar = digits.charAt(index);
        int digit = digitChar - '0';
        String value = map.get(digit);
        for(char ch : value.toCharArray())
        {
            findCombination(digits, index+1, str + ch, result, map);
        }
    }
}

// digits = "34"
// digitChar = '3' map.get('3')="def"