add 1 to all digits in string-CodePudding

I am working on strings and working on a problem. The problem statement is to "add one to all digits inside string".I am not getting desired output for input numbers 129 and 9923. can anyone please help!

import java.util.*;
public class Increment {
  public static void main(String[] args) {
    String number = "129";
    int len = number.length();
    int i = 0;
    int temp = 0;
    int before = 0;
    int carry = 0;

    String result = number;
    for (i = len - 1; i >= 0; i--) {
      temp = Integer.parseInt(number.charAt(i)   "");
      if (temp >= 0 && temp < 9) {
        carry = 0;
        temp = temp   1;
        result = result.replace(number.charAt(i), (char)(temp   '0'));
      } else {
        carry = 1;
        if (i != 0) {
          before = Integer.parseInt(number.charAt(i - 1)   "");
          before = before   1;
          result = result.replace(number.charAt(i), '0');
          result = result.replace(number.charAt(i - 1), (char)(before   carry));
          i = i - 1;
        } else {
          result = result.replace(number.charAt(i), '0');
          result = "1"   result;
        }
      }
    }
    System.out.println(result);
  }
}

CodePudding user response：

You define a method for adding two strings and call that method

public static String addStrings(String num1, String num2) {
  StringBuilder sb = new StringBuilder();

  int i = num1.length() - 1, j = num2.length() - 1;
  int carry = 0, sum = 0;
  while (i >= 0 || j >= 0) {
    sum = carry;

    if (i >= 0) sum  = num1.charAt(i) - '0';
    if (j >= 0) sum  = num2.charAt(j) - '0';

    sb.append(sum % 10);
    carry = sum / 10;
    i--;
    j--;
  }

  if (carry != 0) sb.append(carry);

  return sb.reverse().toString();
}

, main

public static void main(String[] args) {
  String num1 = "129";
  String num2 = "9923";
  String res1 = addStrings(num1, "1".repeat(num1.length()));
  String res2 = addStrings(num2, "1".repeat(num2.length()));

  System.out.println(res1);
  System.out.println(res2);
}

, output

240
11034

CodePudding user response：

I would use regex, it makes it a much simpler solution:

public static void main(String[] args) {
    String text = "text240 moretext 350 evenmore460text";
    Pattern pattern = Pattern.compile("\\d ");

    Matcher matcher = pattern.matcher(text);
    while (matcher.find()) {
        String value = matcher.group();
        int val = Integer.parseInt(value)   1;
        text = text.replace(value, Integer.toString(val));
    }
    System.out.println(text);
}

CodePudding user response：

The problem is this line of code, check here for more info

result = result.replace(number.charAt(i - 1), (char) (before   carry));

You may change it like below, but that would replace all occurrences of first argument

result = result.replace(number.charAt(i - 1), Character.forDigit(before   carry, 10));

So, I would suggest to use StringBuilder instead of String in order to take advantage of the setCharAt(int idx, char c) method