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#include <assert.h> | |
#include <ctype.h> | |
#include <stdio.h> | |
#include <deque> | |
struct Node | |
{ | |
Node(char v) : val(v) {} | |
bool isOperator() const | |
{ | |
return !isalnum(val); | |
} | |
void print() const | |
{ | |
if (isOperator()) | |
{ | |
printf("("); | |
if (left) | |
{ | |
left->print(); | |
} | |
printf(" %c ", val); | |
if (right) | |
{ | |
right->print(); | |
} | |
printf(")"); | |
} | |
else | |
{ | |
printf("%c", val); | |
} | |
} | |
char val; | |
Node* left = NULL; | |
Node* right = NULL; | |
}; | |
Node* buildTree(const char* expr) | |
{ | |
Node* root = NULL; | |
std::deque<Node**> queue; | |
queue.push_back(&root); | |
for (const char* p = expr; *p; ++p) | |
{ | |
assert(!queue.empty()); | |
Node** curr = queue.front(); | |
queue.pop_front(); | |
assert(*curr == NULL); | |
Node* n = new Node(*p); | |
*curr = n; | |
if (n->isOperator()) | |
{ | |
queue.push_back(&n->left); | |
queue.push_back(&n->right); | |
} | |
} | |
assert(queue.empty()); | |
return root; | |
} | |
int main(int argc, char* argv[]) | |
{ | |
Node* root = buildTree(argc > 1 ? argv[1] : "-+a+-abcd"); | |
root->print(); | |
printf("\n"); | |
} |
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