Number of Digit One

Iterate through all numbers from 1 to n and count the number of 1's in each number.

1. Initialize count = 0
2. Loop from i = 1 to n
3. Convert i to string
4. Count '1's in the string
5. Add count to total
6. Return total count

For each number from 1 to n:

1. Convert the number to string
2. Count the occurrences of '1' in the string
3. Add the count to total

public int countDigitOne(int n) {
    int count = 0;
    for (int i = 1; i <= n; i++) {
        String num = String.valueOf(i);
        for (char c : num.toCharArray()) {
            if (c == '1') {
                count++;
            }
        }
    }
    return count;
}