10986 나머지합구하기

import java.util.Scanner;

public class RemainSum {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int M = sc.nextInt();
        long[] S = new long[N];
        long[] C = new long[M];
        long answer = 0;
        S[0] = sc.nextInt(); //합배열

        for(int i=1; i<N; i++) {
            S[i] = S[i-1] + sc.nextInt();
        }
        for(int i=0; i<N; i++) {
            int remainder = (int) (S[i] % M);
            if(remainder == 0) answer ++;
            C[remainder] ++;
        }
        for(int i=0; i<M; i++) {
            if(C[i] > 1) {
                answer = answer + (C[i] * (C[i]-1)/2 );
            }
        }
        System.out.print(answer);
    }
}