Uva——11827 Maximum gcd

迷南。 2022-08-10 15:53 21阅读 0赞

这一题的主要是考察读入数据的技巧，其余的好像就没有了.

关于int ungetc(char c, FILE \*stream);

### Parameters ###

character

The  int promotion of the character to be put back.  
The value is internally converted to an  unsigned char when put back.

stream

Pointer to a  [FILE][] object that identifies an input stream.

### Return Value ###

On success, the character put back is returned.

If the operation fails,  [EOF][]  is returned.

### Example ###

<table style="font-size:12px; color:black"> 
 <tbody> 
  <tr> 
   <td style="color:rgb(160,160,160); text-align:right; vertical-align:top; min-width:20px"> <pre style="margin-top:0px; margin-bottom:0px"><code>1
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</code></pre> </td> 
   <td style="background-color:rgb(239,239,255); border:1px solid rgb(192,192,208); vertical-align:top"> <pre style="margin-top:0px; margin-bottom:0px"><code><cite style="font-style:normal; color:rgb(0,112,0)">/* ungetc example */</cite>
#include &lt;stdio.h&gt;

int main ()
{
  FILE * pFile;
  int c;
  char buffer [256];

pFile = fopen ("myfile.txt","rt");
  if (pFile==NULL) perror ("Error opening file");
  else while (!feof (pFile)) {
    c=getc (pFile);
    if (c == EOF) break;
    if (c == '#') ungetc ('@',pFile);
    else ungetc (c,pFile);
    if (fgets (buffer,255,pFile) != NULL)
      fputs (buffer,stdout);
    else break;
  }
  return 0;
}</code></pre> </td> 
  </tr> 
 </tbody> 
</table>

先是我的比较坑的代码：

#include <stdio.h>
    #include <string.h>
    #include <math.h>
    int gcd(int a,int b)
    {
    	while(b!=0)
    	{
    		int t=b;
    		b=a%b;
    		a=t;
    	}
    	return a;
    }
    int m_pow(int a,int x)
    {
    	int t=1;
    	while(x!=0)
    	{
    		if(x&1)t*=a;
    		a*=a;
    		x>>=1;
    	}
    	return t;
    }
    int num[101];
    char str[300],snum[100][20];
    int main()
    {
    	int n,t;
    	scanf("%d",&t);
    	getchar();
    	while(t--)
    	{
    		int i,j,k,count=-1,len,min;
    		memset(snum,0,sizeof(snum));
    		gets(str);
    		len=strlen(str);
    		for(i=0;i<len;i++)
    		{
    			if((i==0||(i>0&&str[i-1]==' '))&&str[i]!=' ')
    			{
    				k=0;++count;
    				snum[count][k]=str[i];	
    			}
    			else if(str[i]!=' ')
    			{
    				k++;
    				snum[count][k]=str[i];
    			}
    		}
    	//	for(i=0;i<=count;i++)
    	//	printf("%s ",snum[i]);
    		memset(num,0,sizeof(num));
    		for(i=0;i<=count;i++)
    		{
    			k=strlen(snum[i]);
    			for(j=0;j<k;j++)
    			{
    				num[i]+=(snum[i][j]-'0')*m_pow(10,(k-1-j));
    			}
    		}
    	/*	for(i=0;i<=count;i++)
    		printf("%d ",num[i]);
    		printf("\n");*/
    		 min=-1;
    		for(i=0;i<count;i++)
    		for(j=i+1;j<=count;j++)
    		{
    			int temp=gcd(num[i],num[j]);
    			if(min<temp)min=temp;
    		}
    		printf("%d\n",min);
    	}
    }

再是别人的代码，调用了一些函数，处理的很棒

#include<cstdio>  
    #include<algorithm>  
    using namespace std;  
        
    int num[100], n;  
        
    int gcd(int a, int b)  
    {  
        return b ? gcd(b, a % b) : a;  
    }  
        
    int cal()  
    {  
        int i, j, maxn = 0;  
        for (i = 0; i < n - 1; ++i)  
            for (j = i + 1; j < n; ++j)  
                maxn = max(maxn, gcd(num[i], num[j]));  
        return maxn;  
    }  
        
    int main()  
    {  
        int t;  
        char ch;  
        scanf("%dn", &t);  
        while (t--)  
        {  
            n = 0;  
            while (true)  
            {  
                scanf("%d", &num[n++]);  
                while ((ch = getchar()) == ' ');  //读取空格
                ungetc(ch, stdin); //把ch读到的非" "返回到输入流中去
                if (ch == 10 || ch == -1) break;//如果ch为"\n"或EOF则结束读入 
            }  
            printf("%dn", cal());  
        }  
        return 0;  
    }

c++形式：

#include<cstdio>  
    #include<iostream>  
    #include<sstream>  
    #include<string>  
    using namespace std;  
        
    int num[100], n;  
    string s;  
        
    int gcd(int a, int b)  
    {  
        return b ? gcd(b, a % b) : a;  
    }  
        
    int cal()  
    {  
        int i, j, maxn = 0;  
        for (i = 0; i < n - 1; ++i)  
            for (j = i + 1; j < n; ++j)  
                maxn = max(maxn, gcd(num[i], num[j]));  
        return maxn;  
    }  
        
    int main()  
    {  
        int t;  
        scanf("%dn", &t);  
        while (t--)  
        {  
            getline(cin, s);  
            stringstream ss(s); //把string s中的内容存到ss中 
            n = 0;  
            while (ss >> num[n]) // 从ss中取数
                ++n;  
            printf("%dn", cal());  
        }  
        return 0;  
    }

[FILE]: http://www.cplusplus.com/FILE
[EOF]: http://www.cplusplus.com/EOF