if(表達(dá)式)
    語句;

//if(表達(dá)式)
//    語句1;
//else
//    語句2;
int main()
{
	int age = 0;
	scanf("%d", &age);
	if (age >= 18)
		printf("成年\n");
	else
		printf("未成年\n");
	return 0;
}

//多分支    
//if(表達(dá)式1)
//    語句1;
//else if(表達(dá)式2)
//    語句2;
//else
//    語句3;
 int main()
{
	int age = 0;
	scanf("%d", &age);
	if (age < 18)
	{
		printf("青少年\n");
		printf("好好學(xué)習(xí)\n");
	}
	//if與elseif 后面默認(rèn)只能跟一條語句
	else if (age >= 18 && age < 30)//&& 并且
		printf("青年\n");
	else if (age >= 30 && age < 50)
		printf("中年\n");
	else if (age >= 50 && age < 90)
		printf("老年\n");
	else
		printf("老壽星\n");
	return 0;
}

#include <stdio.h>
int main()
{
    if(表達(dá)式)
   {
        語句列表1；
   }
    else
   {
        語句列表2；
   }
    return 0; 
}

//寫法一
#include <stdio.h>
int main()
{
    int a = 0;
    int b = 2;
    if(a == 1)
        if(b == 2)
            printf("hehe\n");
    else
        printf("haha\n");
    return 0; }

//寫法二
#include <stdio.h>
int main()
{
	int a = 0;
	int b = 2;
	if (a == 1)
		if (b == 2)
			printf("hehe\n");
		else
			printf("haha\n");
	return 0;
}

#include <stdio.h>
int main()
{
	int a = 0;
	int b = 2;
	if (a == 1)
	{ 
		if (b == 2)
			printf("hehe\n");
		else
			printf("haha\n");
	}
	return 0;
}

#include <stdio.h>
int main()
{
	int a = 0;
	int b = 2;
	if (a == 1)
	{
		if (b == 2)
			printf("hehe\n");
	}
	else
	{
		printf("haha\n");
	}
			return 0;
}

//condition  條件
//代碼1
if (condition) {
	return x;
}
return y;
//代碼2
if (condition) {
	return x;
}
else
{
	return y;
}

//代碼3
int num = 1;
if (num == 5) {
	printf("hehe\n");
}
//代碼4
int num = 1;
if (5 == num) {
	printf("hehe\n");
}

int main()
{
	int n = 0;
	scanf("%d", &n);
	if (1 == n % 2)
	//或者用if (n % 2 != 0)
	//!= -->  不等于
	{
		printf("奇數(shù)\n");
	}
	return 0;
}

int main()
{
	//打印1~100之間的奇數(shù)
	int i = 1;
	while (i <= 100)
	{
		//對i進(jìn)行判斷，是奇數(shù)才打印
		if(i % 2 == 1)
			printf("%d ", i);
		i++;
	}
	return 0;
}

int main()
{
	int day = 0;
	scanf("%d", &day);
	switch (day)
	{
	case 1:
		printf("星期一\n");
		break;
	case 2:
		printf("星期二\n");
		break;
	case 3:
		printf("星期三\n");
		break;
	case 4:
		printf("星期四\n");
		break;
	case 5:
		printf("星期五\n");
		break;
	case 6:
		printf("星期六\n");
		break;
	case 7:
		printf("星期天\n");
		break;
	}
	return 0;
}

switch(整型表達(dá)式)
{
    語句項(xiàng)；
}

//是一些case語句：
//如下：
case 整形常量表達(dá)式:
    語句;

int main()
{
	int day = 0;
	scanf("%d", &day);
	switch (day)
	{
	case 1:
	case 2:
	case 3:
	case 4:
	case 5:
		printf("工作日\n");
		break;
	case 6:
	case 7:
		printf("休息日\n");
		break;
	default:
		printf("輸入錯誤\n");
		break;
	}
	return 0;
}

int main()
{
	int i = 1;
	while (i <= 10)
	{
		printf("%d ", i);
		i = i + 1;
	}
	return 0;
}

int main()
{
	int i = 1;
	while (i <= 10)
	{
		if (i == 5)
			break;
		printf("%d ", i);
		i = i + 1;
	}
	return 0;
}
//1 2 3 4

//continue 代碼實(shí)例1
int main()
{
	int i = 1;
	while (i <= 10)
	{
		if (i == 5)
			continue;
		printf("%d ", i);
		i = i + 1;
	}
	return 0;
}
//1 2 3 4 _(循環(huán))

//continue 代碼實(shí)例2#include <stdio.h>int main(){int i = 1;while (i <= 10){i = i + 1;if (i == 5)continue;printf("%d ", i);}return 0;}//2 3 4 6 7 8 9 10 11//continue 代碼實(shí)例2
#include <stdio.h>
int main()
{
	int i = 1;
	while (i <= 10)
	{
		i = i + 1;
		if (i == 5)
			continue;
		printf("%d ", i);
	}
	return 0;
}
//2 3 4 6 7 8 9 10 11