C언어 조건문 중복 줄이기: 최적화 팁과 실전 예제

// 중복된 조건문
if (a > 0) {
    if (b > 0) {
        printf("Both a and b are positive.\n");
    }
}

// 최적화된 조건문
if (a > 0 && b > 0) {
    printf("Both a and b are positive.\n");
}

// 중복된 조건문
if (a == 0) {
    printf("a is zero.\n");
} else if (b == 0) {
    printf("b is zero.\n");
}

// 최적화된 조건문
if (a == 0 || b == 0) {
    printf("Either a or b is zero.\n");
}

// 중복된 조건문
if ((x > 0) && (y > 0)) {
    printf("Both x and y are positive.\n");
} else if ((x > 0) && (z > 0)) {
    printf("x and z are positive.\n");
}

// 최적화된 조건문
if (x > 0 && (y > 0 || z > 0)) {
    printf("x is positive and at least one of y or z is positive.\n");
}

// 중복된 조건문
if (x > 0 && y > 0) {
    printf("Both x and y are positive.\n");
}
if (x > 0 && y > 0 && z == 10) {
    printf("Both x and y are positive, and z is 10.\n");
}

// 조건문을 함수로 분리
bool areBothPositive(int x, int y) {
    return x > 0 && y > 0;
}

if (areBothPositive(x, y)) {
    printf("Both x and y are positive.\n");
}
if (areBothPositive(x, y) && z == 10) {
    printf("Both x and y are positive, and z is 10.\n");
}

// 분리하지 않은 경우
if (isHoliday && weather == SUNNY) {
    printf("Let's go to the beach!\n");
}

// 조건을 판단하는 함수
bool shouldGoToBeach(bool isHoliday, int weather) {
    return isHoliday && weather == SUNNY;
}

// 동작 코드
if (shouldGoToBeach(isHoliday, weather)) {
    printf("Let's go to the beach!\n");
}

bool isEven(int number) {
    return number % 2 == 0;
}

if (isEven(a)) {
    printf("a is even.\n");
}
if (isEven(b)) {
    printf("b is even.\n");
}

// if-else로 다중 조건 처리
if (status == 1) {
    printf("Status: Pending\n");
} else if (status == 2) {
    printf("Status: Approved\n");
} else if (status == 3) {
    printf("Status: Rejected\n");
} else {
    printf("Status: Unknown\n");
}

// switch문으로 변경
switch (status) {
    case 1:
        printf("Status: Pending\n");
        break;
    case 2:
        printf("Status: Approved\n");
        break;
    case 3:
        printf("Status: Rejected\n");
        break;
    default:
        printf("Status: Unknown\n");
        break;
}

// 전처리 후 switch 사용
int condition = (isHoliday << 1) | (weather == SUNNY);
switch (condition) {
    case 0:
        printf("Not a holiday and bad weather.\n");
        break;
    case 1:
        printf("Not a holiday but sunny weather.\n");
        break;
    case 2:
        printf("Holiday but bad weather.\n");
        break;
    case 3:
        printf("Holiday and sunny weather!\n");
        break;
}

// 복잡한 조건문
if (mode == 1) {
    printf("Mode: Idle\n");
} else if (mode == 2) {
    printf("Mode: Running\n");
} else if (mode == 3) {
    printf("Mode: Paused\n");
} else {
    printf("Mode: Unknown\n");
}

// 상태 관리 패턴 적용
typedef void (*StateHandler)();

void handleIdle() { printf("Mode: Idle\n"); }
void handleRunning() { printf("Mode: Running\n"); }
void handlePaused() { printf("Mode: Paused\n"); }
void handleUnknown() { printf("Mode: Unknown\n"); }

void processState(int mode) {
    StateHandler handlers[] = {handleUnknown, handleIdle, handleRunning, handlePaused};
    if (mode < 1 || mode > 3) mode = 0;  // Unknown state
    handlers[mode]();
}

#include <stdio.h>

// 상태 정의
typedef enum { IDLE, RUNNING, PAUSED } State;

// 상태 전환 함수
State nextState(State current, int input) {
    switch (current) {
        case IDLE:
            return input == 1 ? RUNNING : IDLE;
        case RUNNING:
            return input == 0 ? PAUSED : RUNNING;
        case PAUSED:
            return input == 1 ? RUNNING : PAUSED;
    }
    return IDLE; // 기본 상태
}

int main() {
    State state = IDLE;
    printf("Initial State: IDLE\n");

    // 상태 전환 테스트
    state = nextState(state, 1); // RUNNING
    printf("Next State: RUNNING\n");

    state = nextState(state, 0); // PAUSED
    printf("Next State: PAUSED\n");
    return 0;
}

// 조건문 사용
if (code == 0) {
    printf("Success\n");
} else if (code == 1) {
    printf("Error\n");
} else if (code == 2) {
    printf("Warning\n");
} else {
    printf("Unknown\n");
}

// 배열로 대체
const char *messages[] = {"Success", "Error", "Warning", "Unknown"};
if (code >= 0 && code < 3) {
    printf("%s\n", messages[code]);
} else {
    printf("%s\n", messages[3]);
}

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

typedef struct {
    const char *key;
    const char *value;
} HashEntry;

// 해시 테이블 정의
HashEntry hashTable[] = {
    {"start", "Starting process..."},
    {"stop", "Stopping process..."},
    {"pause", "Pausing process..."},
    {"resume", "Resuming process..."},
};

const char* getMessage(const char *command) {
    for (int i = 0; i < sizeof(hashTable) / sizeof(HashEntry); i++) {
        if (strcmp(hashTable[i].key, command) == 0) {
            return hashTable[i].value;
        }
    }
    return "Invalid command.";
}

int main() {
    printf("%s\n", getMessage("start")); // Starting process...
    printf("%s\n", getMessage("unknown")); // Invalid command.
    return 0;
}

#include <stdio.h>
#include <stdlib.h>

// 노드 구조체 정의
typedef struct Node {
    int key;
    const char *message;
    struct Node *left, *right;
} Node;

// 새로운 노드 생성
Node* createNode(int key, const char *message) {
    Node *node = (Node *)malloc(sizeof(Node));
    node->key = key;
    node->message = message;
    node->left = node->right = NULL;
    return node;
}

// 이진 탐색 트리에서 메시지 검색
const char* search(Node *root, int key) {
    if (!root) return "Key not found.";
    if (key == root->key) return root->message;
    if (key < root->key) return search(root->left, key);
    return search(root->right, key);
}

int main() {
    // 트리 구성
    Node *root = createNode(10, "Medium priority");
    root->left = createNode(5, "Low priority");
    root->right = createNode(15, "High priority");

    // 검색
    printf("%s\n", search(root, 15)); // High priority
    printf("%s\n", search(root, 7));  // Key not found.
    return 0;
}

if (age >= 0 && age <= 12) {
    printf("Child\n");
} else if (age >= 13 && age <= 19) {
    printf("Teenager\n");
} else if (age >= 20 && age <= 64) {
    printf("Adult\n");
} else if (age >= 65) {
    printf("Senior\n");
} else {
    printf("Invalid age\n");
}

#include <stdio.h>

typedef struct {
    int minAge;
    int maxAge;
    const char *category;
} AgeCategory;

AgeCategory categories[] = {
    {0, 12, "Child"},
    {13, 19, "Teenager"},
    {20, 64, "Adult"},
    {65, 200, "Senior"}
};

const char* getAgeCategory(int age) {
    for (int i = 0; i < sizeof(categories) / sizeof(AgeCategory); i++) {
        if (age >= categories[i].minAge && age <= categories[i].maxAge) {
            return categories[i].category;
        }
    }
    return "Invalid age";
}

int main() {
    int age = 30;
    printf("%s\n", getAgeCategory(age)); // Adult
    return 0;
}

if (status == "active" || status == "enabled" || status == "on") {
    printf("Status is active\n");
}

#include <stdbool.h>
#include <string.h>

bool isActiveStatus(const char *status) {
    return strcmp(status, "active") == 0 || strcmp(status, "enabled") == 0 || strcmp(status, "on") == 0;
}

int main() {
    if (isActiveStatus("enabled")) {
        printf("Status is active\n");
    }
    return 0;
}

// 기존 코드
if ((x > 0 && x < 10) || (x > 20 && x < 30)) {
    printf("x is in the range 1-9 or 21-29.\n");
}

// 기존 코드
if (score >= 90) {
    printf("Grade: A\n");
} else if (score >= 80) {
    printf("Grade: B\n");
} else if (score >= 70) {
    printf("Grade: C\n");
} else {
    printf("Grade: F\n");
}

// 기존 코드
if (code == 1) {
    printf("Option 1 selected.\n");
} else if (code == 2) {
    printf("Option 2 selected.\n");
} else if (code == 3) {
    printf("Option 3 selected.\n");
} else {
    printf("Invalid option.\n");
}

// 기존 코드
if (state == 0) {
    printf("Character is idle.\n");
} else if (state == 1) {
    printf("Character is walking.\n");
} else if (state == 2) {
    printf("Character is running.\n");
} else {
    printf("Unknown state.\n");
}

// 기존 코드
if (status == "open") {
    printf("The file is open.\n");
} else if (status == "closed") {
    printf("The file is closed.\n");
} else if (status == "error") {
    printf("File operation error.\n");
} else {
    printf("Unknown status.\n");
}