求n的阶乘

#include<stdio.h>
int main()
{
  int n;
  int i = 0;
  int m = 1;
  scanf_s("%d", &n);
  for (i = 1; i <= n; i++)
  {
    m = m * i;
  }
  printf("%d\n", m);
  return 0;
}


计算1！+2！+3！+4！+5！+6！+7！+8！+9！+10！

#include<stdio.h>
int main()
{
  int n=0;
  int i = 0;
  int m = 1;
  for (i = 1; i <= 10; i++)
  {
    m = m * i;
    n = n + m;
  }
  printf("%d\n", n);
  return 0;
}

在一个有序数组中查找具体的某个数字n。编写int binsearch（int x，int v[]，int n）；功能：在v[0]<=v[2]<=......<=v[n-1]的数组中查找x。

法1：

#include<stdio.h>
int main()
{
  int arr[] = { 1,2,3,4,5,6,7,8,9,10 };
  int k = 7;
  int i = 0;
  int sz = sizeof(arr) / sizeof(arr[0]);
  for (i = 0; i <= sz; i++)
  {
    if(k==arr[i])
    {
      printf("下标是：%d\n", i);
      break;
    }
  }
  if (i == sz)
    printf("找不到\n");
  return 0;
}

法2：

#include<stdio.h>
int main()
{
  int arr[] = { 1,2,3,4,5,6,7,8,9,10 };
  int k = 7;
  int sz = sizeof(arr) / sizeof(arr[0]);
  int left = 0;//左下标
  int right = sz-1;//右下标
  while (left<=right)
  {
    int mid = (left + right) / 2;
    if (arr[mid] > k)
    {
      right = mid - 1;
    }
    else if (arr[mid] < k)
    {
      left = mid + 1;
    }
    else
    {
      printf("找到了，下标是：%d\n", mid);
      break;
    }
  }
  if (left > right)
  {
    printf("找不到\n");
  }
  return 0;
}