AtCoder. ABC 235 A - Rotate

Problem: AtCoder ABC 235 A — Rotate · 한국어 · 日本語

Given a three-digit decimal number, let its hundreds, tens, and ones digits be A, B, and C. The three left cyclic rotations are ABC, BCA, and CAB; output their sum. These are permutations of the three input digits, so repeated digits and zero are handled without any special cases. For example, input 123 produces 123, 231, and 312, whose sum is 666.

Read the input as a string to retain the three digit positions even when B or C is 0. Convert each character to a digit and evaluate the place values directly: 100A + 10B + C, 100B + 10C + A, and 100C + 10A + B. Their sum is at most 2997, so an int is sufficient. The time and additional space complexities are both O(1).

Java

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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
        String digits = input.readLine();
        int a = digits.charAt(0) - '0';
        int b = digits.charAt(1) - '0';
        int c = digits.charAt(2) - '0';

        int answer = (100 * a + 10 * b + c)
                + (100 * b + 10 * c + a)
                + (100 * c + 10 * a + b);
        System.out.println(answer);
    }
}