(C언어) 3차원배열 성적처리프로그램

#include<stdio.h>
#include<string.h>


int input_int();
int total(int a, int b, int c);
float avg(int total);

void insert();
void select();
void select_all();
void modify();
void delete();

int arr[3][3][3];

int main()
{
	int yn;

	do {
		int choice;

		printf("1.등록 2.조회 3.전체 조회 4.수정 5.삭제");
		choice = input_int();
		switch (choice)
		{
		case 1:
			insert();
			break;
		case 2:
			select();
			break;
		case 3:
			select_all();
			break;
		case 4:
			modify();
			break;
		case 5:
			delete();
			break;
		default:
			break;
		}

		printf("계속하시겠습니까?\n");
		printf("99.끝내기 나머지.계속\n");
		yn = input_int();

	} while (yn != 99);
}

void insert() 
{
	printf("반 : ");
	int classNum = input_int();
	printf("학생 : ");
	int student = input_int();

	for (int i = 0; i < 3; i++) {
		if (arr[classNum][student][i] != 0) {
			printf("해당 학생이 이미 존재합니다.\n");
			return;
		}
		printf("점수를 입력해주세요 :");
		arr[classNum][student][i] = input_int();
	}
}

void select() 
{
	printf("반 : ");
	int classNum = input_int();
	printf("학생 : ");
	int student = input_int();
	
	int kor = arr[classNum][student][0];
	int eng = arr[classNum][student][1];
	int math = arr[classNum][student][2];
	int score_total = total(kor, eng, math);
	float average = avg(score_total);
	printf("%d반 %d번 학생 -> ", classNum, student);
	printf("국어:%d 영어:%d 수학:%d 총점:%d 평균:%f\n", kor, eng, math, score_total, average);

}

void select_all() 
{
	for (int i = 0; i < 3; i++) {
		for (int j = 0; j < 3; j++) {
			int kor = arr[i][j][0];
			int eng = arr[i][j][1];
			int math = arr[i][j][2];
			int score_total = total(kor, eng, math);
			float average = avg(score_total);
			printf("%d반 %d번 학생 -> ",i, j);
			printf("국어:%d 영어:%d 수학:%d 총점:%d 평균:%f\n", kor, eng, math, score_total, average);
		}
	}
}

void modify()
{
	printf("반 : ");
	int classNum = input_int();
	printf("학생 : ");
	int student = input_int();

	printf("국어 점수를 입력해주세요 \n");
	arr[classNum][student][0] = input_int();
	printf("영어 점수를 입력해주세요 \n");
	arr[classNum][student][1] = input_int();
	printf("수학 점수를 입력해주세요 \n");
	arr[classNum][student][2] = input_int();
}

void delete() 
{
	printf("반 : ");
	int classNum = input_int();
	printf("학생 : ");
	int student = input_int();

	arr[classNum][student][0] = 0;
	arr[classNum][student][1] = 0;
	arr[classNum][student][2] = 0;
}

int input_int() 
{
	int i;
	scanf_s("%d", &i);
	return i;
}

int total(int a, int b, int c)
{
	return (a + b + c);
}

float avg(int total)
{
	return (total / 3.f);
}