#include <stdio.h>
int main()
{
    int arr[] = { 1,2,3,4,5,6,7,8,9,10,11,12,13 };
    int left = 0, right = sizeof(arr) / sizeof(arr[0]) - 1;
    int x = 0,flag = 0;
 
    scanf("%d", &x);//要找的數(shù)
 
    while (left <= right)//若要找的數(shù)在此數(shù)組中，此條件會一直成立；
                         //若要找的數(shù)不在此數(shù)組中，最終left會大于right,從循環(huán)中跳出
    {
        int mid = (left + right) / 2;
        if (x == arr[mid])
        {
            printf("%d\n", mid);
            flag = 1;
            break;
        }
        else if (x > arr[mid])
        {
            left = mid + 1;
        }
        else
        {
            right = mid - 1;
        }
    }
    if (flag == 0)//只有當要找的數(shù)在數(shù)組中找不到時flag == 0
    {
        printf("找不到\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;
}

#include <stdio.h>
int main()
{
	int n = 1;
	int m = 2;
	switch (n)
	{
	case 1:
		m++;//m == 3
	case 2:
		n++;//n == 2
	case 3:
		switch (n)
		{//switch允許嵌套使用
		case 1:
			n++;
		case 2:
			m++;//m == 4
			n++;//n == 3
			break;
		}
	case 4:
		m++;//m == 5, n == 3
		break;
	default:
		break;
	}
	printf("m = %d, n = %d\n", m, n);
	return 0;
}