算法3 ----二分法查找

查找一个有序数组中的某个元素

void main()
{
 int a[103];
 //创建一个有序的数组
 for (int i = 0; i < 103; i++)
 {
  a[i] = i;
 }
 
 int num = 52;   //需要查找的元素
 int shang = 0;
 int xia = 102;
 int zhong;
 while (shang < xia)
 {
  zhong = (shang + xia) / 2;
  printf("shang = %d,zhong = %d,xia = %d\n", shang, zhong, xia);
  if (a[zhong] == num )
  {
   printf("找到了");
   break;
  }
  else if (a[zhong] > num)
  {
   xia = zhong - 1;
  }
  else  //a[zhong] < num
  {
   shang = zhong + 1;
  }
 }
 system("pause");
}