src/main/java/com/fishercoder/solutions/_1432.java

package com.fishercoder.solutions;

public class _1432 {
    public static class Solution1 {
        public int maxDiff(int num) {
            int smallest = getSmallest(num);
            int biggest = getBiggest(num);
            return biggest - smallest;
        }

        private int getBiggest(int num) {
            int firstDigit = Integer.parseInt(Integer.toString(num).substring(0, 1));
            if (firstDigit == 9) {
                String remainder = Integer.toString(num).substring(1);
                int numberToChangeToNine = 0;
                for (char c : remainder.toCharArray()) {
                    if (c == '9') {
                        continue;
                    } else {
                        numberToChangeToNine = Integer.parseInt("" + c);
                        break;
                    }
                }
                StringBuilder sb = new StringBuilder();
                sb.append('9');
                for (char c : remainder.toCharArray()) {
                    if (Integer.parseInt(c + "") == numberToChangeToNine) {
                        sb.append("9");
                    } else {
                        sb.append(c);
                    }
                }
                return Integer.parseInt(sb.toString());
            } else {
                int numberToChangeToNine = firstDigit;
                StringBuilder sb = new StringBuilder();
                for (char c : Integer.toString(num).toCharArray()) {
                    if (Integer.parseInt("" + c) == numberToChangeToNine) {
                        sb.append("9");
                    } else {
                        sb.append(c);
                    }
                }
                return Integer.parseInt(sb.toString());
            }
        }

        private int getSmallest(int num) {
            int firstDigit = Integer.parseInt(Integer.toString(num).substring(0, 1));
            if (firstDigit == 1) {
                String remainder = Integer.toString(num).substring(1);
                int numberToChangeToZero = 0;
                for (char c : remainder.toCharArray()) {
                    if (c == '0' || c == '1') {
                        continue;
                    } else {
                        numberToChangeToZero = Integer.parseInt("" + c);
                        break;
                    }
                }
                StringBuilder sb = new StringBuilder();
                sb.append('1');
                for (char c : remainder.toCharArray()) {
                    if (Integer.parseInt(c + "") == numberToChangeToZero) {
                        sb.append("0");
                    } else {
                        sb.append(c);
                    }
                }
                return Integer.parseInt(sb.toString());
            } else {
                int numberToChangeToOne = firstDigit;
                StringBuilder sb = new StringBuilder();
                for (char c : Integer.toString(num).toCharArray()) {
                    if (Integer.parseInt("" + c) == numberToChangeToOne) {
                        sb.append("1");
                    } else {
                        sb.append(c);
                    }
                }
                return Integer.parseInt(sb.toString());
            }
        }
    }
}