코딩 테스트

1. 백준 10986

[풀이]

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

public class Main{
    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        StringTokenizer st = new StringTokenizer(br.readLine());
        int numN = Integer.parseInt(st.nextToken());
        int numM = Integer.parseInt(st.nextToken());

        int[][] numS = new int[numN+1][numN+1];
        int j = 0;

        for (int i = 1; i <= numN * numN; i++) {
            int num = i%numN;

            if (num == 1) {
                st = new StringTokenizer(br.readLine());
                j++;
            }

            if (num == 0) {
                num = numN;
            }

            numS[j][num] = numS[j][num-1] + Integer.parseInt(st.nextToken());
        }

        int[] results = new int[numM];

        for (int i = 0; i < numM; i++) {
            st = new StringTokenizer(br.readLine());
            int x1 = Integer.parseInt(st.nextToken());
            int y1 = Integer.parseInt(st.nextToken());
            int x2 = Integer.parseInt(st.nextToken());
            int y2 = Integer.parseInt(st.nextToken());

            for (j = x1; j <= x2; j++) {
                results[i] += numS[j][y2] - numS[j][y1-1];
            }
        }

        for (int result : results) {
            System.out.println(result);
        }
    }
}

[다른풀이]

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

public class Main{
    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        StringTokenizer st = new StringTokenizer(br.readLine());
        int numN = Integer.parseInt(st.nextToken());
        int numM = Integer.parseInt(st.nextToken());

        int[][] numS = new int[numN+1][numN+1];
        int j = 0;

        for (int i = 1; i <= numN * numN; i++) {
            int num = i%numN;

            if (num == 1) {
                st = new StringTokenizer(br.readLine());
                j++;
            }

            if (num == 0) {
                num = numN;
            }

            numS[j][num] = numS[j][num-1] + numS[j-1][num] - numS[j-1][num-1] + Integer.parseInt(st.nextToken());
        }

        int[] results = new int[numM];

        for (int i = 0; i < numM; i++) {
            st = new StringTokenizer(br.readLine());
            int x1 = Integer.parseInt(st.nextToken());
            int y1 = Integer.parseInt(st.nextToken());
            int x2 = Integer.parseInt(st.nextToken());
            int y2 = Integer.parseInt(st.nextToken());

            results[i] = numS[x2][y2] - numS[x1-1][y2] - numS[x2][y1-1] + numS[x1-1][y1-1];
        }

        for (int result : results) {
            System.out.println(result);
        }
    }
}

---

2. 백준 10986

(A+B)%C는 ((A%C) +(B%C) %C 와 같다

nCr = n! / (n-r)! / r!

[풀이] 타임아웃

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

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());

        int numN = Integer.parseInt(st.nextToken());
        int numM = Integer.parseInt(st.nextToken());

        long[] numS = new long[numN + 1];

        st = new StringTokenizer(br.readLine());
        for (int i = 1; i <= numN; i++) {
            numS[i] = numS[i - 1] + Long.parseLong(st.nextToken());
        }

        int result = 0;

        for (int i = numN; i > 0; i--) {
            for (int j = i - 1; j >= 0; j--) {
                if ((numS[i] - numS[j]) % numM == 0) {
                    result++;
                }
            }
        }
        System.out.println(result);
    }
}

[다른풀이]

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

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());

        int numN = Integer.parseInt(st.nextToken());
        int numM = Integer.parseInt(st.nextToken());

        long[] numS = new long[numN + 1];
        long[] count = new long[numM];

        st = new StringTokenizer(br.readLine());
        for (int i = 1; i <= numN; i++) {
            numS[i] = numS[i - 1] + Integer.parseInt(st.nextToken());
            long number = numS[i] % numM;
            count[(int) number]++;
        }

        long result = count[0];

        for (int i = 0; i < numM; i++) {
            if (count[i] > 1) {
                result += count[i] * (count[i] - 1) / 2;
            }
        }
        System.out.println(result);
    }
}