How to determine how many times a character is repeated in a string?-CodePudding

I am having some trouble with writing a method that when prompted with a number returns how many times each value is repeated. For example, if the number 7846597 is entered the method would return:

I know this would be most easily done with a loop, but I am not sure how to write the actual code. I also know that I need to convert the number value I get as an input into a string so I can use char methods.

This is my attempt:

public double countOccurences(int num)
{
    String str = num   "";
    int goneThrough = 0;
    int count0 = 0;
    int count1 = 0;
    int count2 = 0;
    int count3 = 0;
    int count4 = 0;
    int count5 = 0;
    int count6 = 0;
    int count7 = 0;
    int count8 = 0;
    int count9 = 0;
    while(goneThrough <= str.length())
    {
        int value = 0;
        if(value >= 10){
            value = value * 0;
        }
        if(str.charAt(0) == 0)
            count0  ;
        if(str.charAt(0) = 1)
            count1  ;
    }
    return count0;
    return count1;
    return count2;
    return count3;
    return count4;
    return count5;
    return count6;
    return count7;
    return count8;
    return count9;
}

CodePudding user response：

countOccurences(int num) should return the number of occurrences of each digit as int[10].

static int[] countOccurences(int num) {
    int[] result = new int[10];
    for ( ; num > 0; num /= 10)
          result[num % 10];
    return result;
}

public static void main(String[] args) {
    int input = 7846597;
    int[] output = countOccurences(input);
    for (int i = 0; i < 10;   i)
        System.out.println(i   " - "   output[i]);
}

output:

CodePudding user response：

This is my code where I used HashTable and stored number as string and count as value. This is optimized code where time complexity is O(n).

// code
import java.util.*;

class Main {  
  public static void main(String args[]) { 
    String number = "7846597";
    Hashtable<String, Integer> result = new Hashtable<String, Integer>();
    
    for(int i=0; i<number.length(); i  ){
        String current = ""   number.charAt(i);
        if(result.contains(current))   {
          int val = result.get(current);
          result.put(current,   val);
        } else {
          result.put(current, 1);
        }
    }
    System.out.print(result);
  } 
}

CodePudding user response：

Using int array of size 10 and increment value at index that maps to digit of 0-9.

public static void digitFrequencies(int number) {
    int[] arr = new int[10];

    for (char ch : String.valueOf(number).toCharArray()) {
      int digit = Character.digit(ch, 10);
      arr[digit] = arr[digit]   1;
    }

    for (int i = 0; i < arr.length; i  ) {
      System.out.print(i   " - "   arr[i]   " ");
    }
  }