有15个数按由小到大的顺序存放在一个数组中，输入一个数，用折半查找法找出它是数组中的第几个元素的值。如果不在的话，就打印“没有找到”

[nothingiknow]

在我的教材里看到的这个程序，怎么运行时，如果数组里有的数就正确呢？ 当数组里没有这个数时运行就不正确了？就不能按照要求显示！这是怎么回事啊？请教下！谢谢各位
#define N 15
void main()
{ int i,num,top,bott,mid,loca,a[N],flag=1,sign=1;
char c;
printf("Enter data:\n");
scanf("%d",&a[0]);
i=1;
while(i<N)
{scanf("%d",&a[i]);
if(a[i]>=a[i-1])
i++;
else
printf("Enter the data again:");
}
printf("\n");
for(i=0;i<N;i++)
printf("%4d",a[i]);
printf("\n");
flag=1;
while(flag)
{printf("Input number to look for:");
scanf("%d",&num);
loca=0;
top=0;
bott=N-1;
if((num<a[0])||(num>a[N-1]))
loca=-1;
while((sign==1)&&(top<=bott))
{mid=(top+bott)/2;
if(num==a[mid])
{loca=mid;
printf("Find %d, its position is %d\n",num,loca+1);
sign=0;
}
else if(num<a[mid])
bott=mid-1;
else
top=mid+1;
}
if(sign==1||loca==-1)
printf("%d is not found.\n",num);
printf("Continue or not (Y/N)?");
scanf("%c",&c);
if(c=='N'||c=='n')
flag=0;
}
}

[srq1625]

#include<stdio.h>//你注意到你的程序里其实没有文件头。

#define N 15
void main()
{ int i,num,top,bott,mid,loca,a[N],flag=1,sign=1;
char c;
printf("Enter data:\n");
scanf("%d",&a[0]);
i=1;
while(i <N)
{
scanf("%d",&a[i]);
if(a[i]>=a[i-1])
i++;
else
printf("Enter the data again:");
}
printf("\n");
for(i=0;i <N;i++)
printf("%4d",a[i]);
printf("\n");
flag=1;
while(flag)
{printf("Input number to look for:");
scanf("%d",&num);
loca=0;
top=0;
bott=N-1;
if((num <a[0])||(num> a[N-1])) //这里的“或”运算符你要注意啊。你写的错了。
loca=-1;
while((sign==1)&&(top <=bott))
{mid=(top+bott)/2;
if(num==a[mid])
{loca=mid;
printf("Find %d, its position is %d\n",num,loca+1);
sign=0;
}
else if(num <a[mid])
bott=mid-1;
else
top=mid+1;
}
if(sign==1||loca==-1)
printf("%d is not found.\n",num);
printf("Continue or not (Y/N)?");
scanf("%c",&c);
if(c=='N' ||c=='n')
flag=0;
}
}
我运行了一下，好了。继续加油啊，o(∩_∩)o...

[nothingiknow]

谢谢哈

[san_dan]

#include <stdio.h>
#include <iostream.h> //下面用到了cin
#define N 15
void main()
{ int i,num,top,bott,mid,loca,a[N],flag=1,sign=1;
char c;
printf("Enter data:\n");
scanf("%d",&a[0]);
i=1;
while(i <N)
{
scanf("%d",&a[i]);
if(a[i]> =a[i-1])
i++;
else
printf("Enter the data again:");
}
printf("\n");
for(i=0;i <N;i++)
printf("%4d",a[i]);
printf("\n");
flag=1;
while(flag)
{printf("Input number to look for:");
scanf("%d",&num);
loca=0;
top=0;
bott=N-1;
if((num <a[0]) ¦ ¦(num> a[N-1]))
loca=-1;
while((sign==1)&&(top <=bott))
{mid=(top+bott)/2;
if(num==a[mid])
{loca=mid;
printf("Find %d, its position is %d\n",num,loca+1);
sign=0;
}
else if(num <a[mid])
bott=mid-1;
else
top=mid+1;
}
if(sign==1 ¦ ¦loca==-1)
printf("%d is not found.\n",num);
sign=1; //我觉得这里要加上这条,要不然下面选Y时不能执行到正确结果
printf("Continue or not (Y/N)?");
cin>>c; //这里用scanf("%c",&c);起不到选择的效果.
if(c=='N' ¦ ¦c=='n')
flag=0;
}
}