\n public class GoodNumber {\n public static void main(String[] args) {\n int N = 23; \/\/ Set the value of N to test here.\n int result = findGoodNumber(N);\n System.out.println(\"The 'good number' is: \" + result);\n }\n\n public static int findGoodNumber(int N) {\n for (int i = N - 1; i > 0; i--) {\n if (digitSum(i) < N) {\n return i; \/\/ Return the largest 'good number'\n }\n }\n return -1; \/\/ Return -1 if not found\n }\n\n public static int digitSum(int num) {\n int sum = 0;\n while (num > 0) {\n sum += num % 10; \/\/ Add each digit\n num \/= 10; \/\/ Divide by 10 to reduce the number of digits\n }\n return sum;\n }\n }\n <\/code>\n <\/pre>\nCode Explanation<\/h2>\n
\n In the Java code above, the main method sets the value of N, then calls the findGoodNumber<\/code> method to find the ‘good number’.
\n The findGoodNumber<\/code> method starts from N-1 and calculates the sum of the digits, returning the number if that value is less than N.\n <\/p>\n\ndigitSum<\/code> method contains the logic to calculate the sum of each digit of the given number.
\n This method uses a loop to separate the digits one by one and returns the summed result.\n <\/p>\nTime Complexity Analysis<\/h2>\n
\n The time complexity of this algorithm is O(N * D), where N is the input value and D is the number of digits in N.
\n It requires O(D) operations to sum the digits for each number, resulting in a worst-case time complexity of O(N * D).\n <\/p>\n
Space Complexity<\/h2>\n
\n The space complexity is O(1). It does not use additional space, and only the input\/output variables and constant space within methods are used,
\n thus minimizing the memory used.\n <\/p>\n
Conclusion and Tips<\/h2>\n
\n The problem of finding a ‘good number’ can be easily solved through a simple loop and digit sum process.
\n However, if N is very large, performance degradation may be a concern, so algorithm optimization may be necessary.
\n Testing this problem with various input values and attempting to solve it with different methods or structures can be a good learning experience.\n <\/p>\n
\n Finally, it is important to practice these types of problems thoroughly while preparing for coding tests.
\n Facing new problems every time and cultivating diverse thinking skills will greatly assist in job preparation.\n <\/p>\n
<\/body><\/p>\n","protected":false},"excerpt":{"rendered":"
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