二分查找

#include <stdio.h>
int main()
{
  int arr[] = { 1,2,3,4,5,6,7,8,9,10 };
  int k = 4;
  int sz = sizeof(arr) / sizeof(arr[0]);  //计算元素个数
  int left = 0;
  int right = sz - 1;
  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");
  }
  return 0;
}