我正在尝试从后缀表达式创建一个解析树。但它给了我分段错误。
这是我的代码:
#include <iostream>
#include <stack>
#include <string>
#include <set>
#include <vector>
#include <cstdio>
#include <queue>
#include <list>
using namespace std;
struct my_tree{
struct my_tree* left;
char a;
struct my_tree* right;
};
typedef struct my_tree TREE;
bool is_binary_op(char a){
if(a == '|' || a == '.') return true;
else return false;
}
bool is_unary_op(char a){
if(a == '*') return true;
else return false;
}
int main() {
string postfix = "ab|*a.b.";
stack<TREE*> parse_tree;
for(unsigned i=0; i<postfix.length(); i++){
if(is_binary_op(postfix[i])){
TREE* n;
TREE* right = parse_tree.top();
parse_tree.pop();
TREE* left = parse_tree.top();
parse_tree.pop();
n->left = left;
n->a = postfix[i];
n->right = right;
parse_tree.push(n);
} else if(is_unary_op(postfix[i])){
TREE* n;
TREE* left = parse_tree.top();
parse_tree.pop();
n->left = left;
n->a = postfix[i];
n->right = NULL;
parse_tree.push(n);
} else{
TREE* n;
n->left = NULL;
n->a = postfix[i];
n->right = NULL;
parse_tree.push(n);
}
}
return 0;
}
答案 0 :(得分:1)
修改所有
TREE *n;
到
TREE *n = new TREE;
因为它们似乎都是树上的新节点。您需要按operator new
分配实际实例。