# scanf返回值问题

pta平台scanf在平台给的样例里怎么解决ignoring return value of ‘scanf’, declared with attribute warn_unused_result 的问题。
a.c:43:5: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &N);
^~~~~~~

## include <stdlib.h>

typedef int ElementType;
typedef struct TNode *Position;
typedef Position BinTree;
struct TNode{

``````ElementType Data;
BinTree Left;
BinTree Right;``````

};

void PreorderTraversal( BinTree BT ); / 先序遍历，由裁判实现，细节不表 /
void InorderTraversal( BinTree BT ); / 中序遍历，由裁判实现，细节不表 /

BinTree Insert( BinTree BST, ElementType X );
BinTree Delete( BinTree BST, ElementType X );
Position Find( BinTree BST, ElementType X );
Position FindMin( BinTree BST );
Position FindMax( BinTree BST );

int main()
{

``````BinTree BST, MinP, MaxP, Tmp;
ElementType X;
int N, i;

BST = NULL;
scanf("%d", &N);
for ( i=0; i<N; i++ ) {
scanf("%d", &X);
BST = Insert(BST, X);
}
printf("Preorder:"); PreorderTraversal(BST); printf("\n");
MinP = FindMin(BST);
MaxP = FindMax(BST);
scanf("%d", &N);
for( i=0; i<N; i++ ) {
scanf("%d", &X);
Tmp = Find(BST, X);
else {
printf("%d is found\n", Tmp->Data);
if (Tmp==MinP) printf("%d is the smallest key\n", Tmp->Data);
if (Tmp==MaxP) printf("%d is the largest key\n", Tmp->Data);
}
}
scanf("%d", &N);
for( i=0; i<N; i++ ) {
scanf("%d", &X);
BST = Delete(BST, X);
}
printf("Inorder:"); InorderTraversal(BST); printf("\n");

return 0;``````

}
/ 你的代码将被嵌在这里 /

BinTree Insert( BinTree BST, ElementType X )
{

``````if(!BST){
BST=malloc(sizeof(struct TNode));
BST->Data=X;
BST->Left=BST->Right=NULL;
}
else if(X < BST->Data)
{
BST->Left=Insert(BST,X);
}
else if(X > BST->Data)
{
BST->Right=Insert(BST,X);
}
return BST;``````

}
//插入
Position Find( BinTree BST, ElementType X )
{

``````if(!BST){return NULL;}
if(X > BST->Data){return Find(BST->Right,X);}
if(X < BST->Data){return Find(BST->Left,X);}
else return BST;``````

}
//查找
Position FindMin( BinTree BST )
{

``````if(!BST){return NULL;}
else if(!BST->Left){
return BST;
}
else return FindMin(BST->Left);``````

}
//找最小
Position FindMax( BinTree BST )
{

``````if(!BST){return NULL;}
else if(!BST->Right){
return BST;
}
else return FindMax(BST->Right);``````

}
//找最大
//删除delete
BinTree Delete(BinTree BST,ElementType X)
{

``````Position temp;
if(!BST)
return BST;
}
else if(X < BST->Data)
{               BST->Left = Delete(BST->Left,X);
}
else if(X > BST->Data){
BST->Right = Delete(BST->Right,X);
}
else
if(BST->Left&&BST->Right)
{
temp = FindMin(BST->Right);
BST->Data = temp->Data;
BST->Right = Delete(BST->Right,BST->Data);

}else{temp=BST;
if(!BST->Left)
BST = BST->Right;
else if(!BST->Left)
BST=BST->Left;
free(temp);
}
return BST;``````

}

2 个回答