c++ - 在声明的行看到未声明的错误

Question

我在声明 rightTree 的那一行收到编译器错误“rightTree is not declared yet”...

此外，当我还在上面声明了 Tree 时，它​​说“Tree does not name a type”...

与 leftTree 相同的情况...

代码:

#include<bits/stdc++.h>
using namespace std;

struct Tree;
struct Node;

long int max(long int a,long int b){
    if(a>=b){
        return a;
    }else{
        return b;
    }
}

struct Node{
    long int value;
    int left_index;
    int right_index;
    Node* left_child;
    Node* right_child;
};

struct Tree{
    Node* root;
    int start;
    int end;
};

Tree* createTree(Node* root,int start,int end){
    Tree* T=new Tree;
    T->root=root;
    T->start=start;
    T->end=end;
    return T;
}

Node* createNode(long value,int left_index,int right_index){
    Node* node=new Node;
    node->value=value;
    node->left_index=left_index;
    node->right_index=right_index;
    node->left_child=NULL;
    node->right_child=NULL;
    return node;
}

void printNode(Node* node){
    cout<<"The value is: "<<node->value<<endl;
    cout<<"Left index is: "<<node->left_index<<endl;
    cout<<"Right index is: "<<node->right_index<<endl;
    if(node->left_child!=NULL){
        cout<<"Left child value is: "<<node->left_child->value<<endl;
    }
    if(node->right_child!=NULL){
        cout<<"Right child value is: "<<node->right_child->value<<endl;
    }
    return;
}

Tree* mergeTree(Node** nodes,Tree* Tree,int start,int end){
    int i;
    /*for(i=0;i<=end;i++){
        cout<<"--\nNode "<<i<<endl;
        printNode(nodes[i]);
    }*/
    if(start>end){
        cout<<"Found start>end..."<<endl;
        Tree=nullptr;
        return Tree;
    }else if(start==end){
        Tree->root=nodes[start];
        Tree->start=start;
        Tree->end=end;
        return Tree;
    }else if(end==start+1){
        if(nodes[start]->value==max(nodes[start]->value,nodes[end]->value)){
            Tree->root=nodes[start];
        }else{
            Tree->root=nodes[end];
        }
        Tree->start=start;
        Tree->end=end;
        return Tree;
    }
    //base case
    int mid=(start+end)/2;

    Tree* rightTree=new Tree;
    rightTree=mergeTree(nodes,rightTree,start,mid);

    Tree* leftTree=new Tree;
    leftTree=mergeTree(nodes,leftTree,mid+1,end);

    Node* root=new Node;
    if(rightTree->root->value==max(rightTree->root->value,leftTree->root->value)){
        root=rightTree->root;
    }else{
        root=leftTree->root;
    }
    root->left_child=leftTree->root;
    root->right_child=leftTree->root;
    //Node* root=new Node;
    return createTree(root,start,end);
}

Tree* segmentTree_form(int a[],int n){
    int i=0;
    Node** nodes=(Node**)malloc(n*sizeof(Node*));
    for(i=0;i<n;i++){
        nodes[i]=createNode(a[i],i,i);
    }
    //Leaf Nodes created.
    /*for(i=0;i<n;i++){
        cout<<"--\nNode "<<i<<endl;
        printNode(nodes[i]);
    }*/
    Tree* T=new Tree;
    T=mergeTree(nodes,T,0,n-1);
    return T;
}

int main() {
    Tree* segmentTree=new Tree;
    int n;
    cin>>n;
    int a[n],i=0;
    for(i=0;i<n;i++){
        cin>>a[i];
    }
    segmentTree=segmentTree_form(a,n);

    //Node* node=createNode(-1,0,0);
    //printNode(node);
    return 0;
}

编译器消息:

prog.cpp: In function 'Tree* mergeTree(Node**, Tree*, int, int)':
prog.cpp:88:11: error: 'rightTree' was not declared in this scope
     Tree* rightTree=new Tree;
           ^
prog.cpp:88:25: error: 'Tree' does not name a type
     Tree* rightTree=new Tree;
                         ^
prog.cpp:91:11: error: 'leftTree' was not declared in this scope
     Tree* leftTree=new Tree;
           ^
prog.cpp:91:24: error: 'Tree' does not name a type
     Tree* leftTree=new Tree;
                        ^

在此先感谢您的帮助....

我写了一段代码，用于从复杂度为 O(logn) 的数组构建分割树我无法调试此错误。我在网上找了它，它说要在上面声明 Tree 和 Node 但这也不起作用。

此外，在编写 Node* node=new Node;没有显示错误。

Answer 1

Tree* mergeTree(Node** nodes,Tree* Tree,int start,int end)

您必须重命名第二个参数。参数名称隐藏了类型名称。