C语言基础练习之数组

1，字符串的循环移动

#include <stdio.h>
#include <string.h>
void func(char buf[], int steps)
{
int i = 0, j = 0, lenth = 0;
char temp = 0;
lenth = strlen(buf);
for (i=0; i<steps; i++)  // 等同于 while (steps--)
{
temp = buf[lenth-1];
for (j=lenth-1; j>0; j--)
{
buf[j] = buf[j-1];
}
buf[0] = temp;
}
}

int main(void)
{
char buf[] = "123456789";
int steps = 0;
printf("输入要移动的位数：");
scanf("%d", &steps);
printf("buf = [%s].\n", buf);
func(buf, steps);
printf("buf = [%s].\n", buf);
return 0;
}

2，数组的首位对调排序

#include <stdio.h>
void func(int arr[], int lenth)
{
int i = 0, temp = 0;
for (i=0; i<lenth/2; i++)
{
temp = arr[lenth-1-i];
arr[lenth-1-i] = arr[i];
arr[i] = temp;
}
}
int main(void)
{
int i = 0;
int arr[5] = {1, 2, 3, 4, 5};
//调用函数，首尾元素对调{5, 4, 3, 2, 1}
func(arr, 5);
for (i=0; i<5; i++)
{
printf("arr[%d] = %d\n",i,arr[i]);
}
return 0;
}

3，二分法查找有序特定元素列

//正确返回数组下标，没有这个数返回-1.
int search_arr_element(int arr[], int left, int right, int data)
{
//定义保存中间下标的变量
int mid = 0;
while (left <= right)
{
//中间下标赋值
mid = (left + right) / 2;
//比较符合条件的下标
if ( data > arr[mid])
{
left = mid + 1;
}
else if (data < arr[mid])
{
right = mid - 1;
}
else
{
printf("找到了%d下标%d.\n", data, mid);
return mid;
}

}
printf("%d查无此数.\n", data);
return -1;
}
int main(void)
{
int arr[5] = {2, 5, 8, 11, 13};
search_arr_element(arr, 0, 4, 11);
return 0;
}

递归的方式(二分法)

void search(int arr[], int left, int right, int data)
{
int mid = (left + right) / 2;
//回归条件（得到正确结果）
if (data == arr[mid])
{
printf("找到数组下标%d的数据%d.\n", mid, data);

return mid;
}
//回归条件（得到非正确结果）
if (left > right)
{
printf("找不到数据%d.\n", data);
return;
}
if (data > arr[mid])
{
search(arr, mid+1, right, data);
}

if (data < arr[mid])
{
search(arr, left, mid-1, data);
}
}