题目链接：http://poj.org/problem?id=1002
思路分析：先对输入字符进行处理，转换为标准形式；插入标准形式的电话号码到查找树中，若有相同号码计数器增加1，再中序遍历查找树。
代码如下：
#include <stdio.h>
#include <stdlib.h>
#include <string.h> struct TreeNode;
typedef char ElementType[];
typedef struct TreeNode *Position;
typedef struct TreeNode *SearchTree;
struct TreeNode
{
int Count;
ElementType Element;
SearchTree Left;
SearchTree Right;
}; void StrToNum( char *str , char * Tel );
SearchTree MakeEmpty( SearchTree T );
SearchTree Insert( ElementType X, SearchTree T );
void PrintTel( SearchTree T );
int flag = ; int main()
{
int n;
char Str[], Tel[];
SearchTree T = NULL; menset( Tel, , sizeof(Tel) ); scanf( "%d", &n );
for ( int i = ; i < n; ++i )
{
scanf( "%s", Str );
StrToNum( Str, Tel );
T = Insert( Tel, T );
} PrintTel( T );
if ( flag == )
printf( "No duplicates.\n" ); return ;
} void PrintTel( SearchTree T )
{
if ( T != NULL )
{
PrintTel( T->Left );
if ( T->Count > )
{
printf( "%s %d\n", T->Element, T->Count );
flag = ;
}
PrintTel( T->Right );
}
} SearchTree MakeEmpty( SearchTree T )
{
if ( T != NULL )
{
MakeEmpty( T->Left );
MakeEmpty( T->Right );
free( T );
}
return NULL;
} SearchTree Insert( ElementType X, SearchTree T )
{
if ( T == NULL )
{
T = ( Position )malloc( sizeof( struct TreeNode ) );
if ( T == NULL )
{
printf( "Out of space" );
return NULL;
}
else
{
strcpy( T->Element, X );
T->Left = T->Right = NULL;
}
}
else
if ( strcmp(X, T->Element) < )
T->Left = Insert( X, T->Left );
else
if ( strcmp(X, T->Element) > )
T->Right = Insert( X, T->Right); return T;
} void StrToNum( char *str , char * Tel )
{
int i, j; for ( i = j = ; str[i] != '\0'; i++ )
{
if ( str[i] == '-' );
else
if ( '' <= str[i] && str[i] <= '' )
Tel[j++] = str[i];
else
if ( str[i] < 'Q' )
Tel[j++] = ( str[i] - 'A' ) / + + '';
else
Tel[j++] = ( str[i] - 'A' - ) / + + ''; if ( j == )
Tel[j++] = '-';
}
}