| 标题 | C++二叉树计算表达式 |
| 范文 | C++二叉树计算表达式，具体代码如下： #include <iostream> using namespace std; class calc { enum Type {DATA, ADD, SUB, MULTI, DIV, OPAREN, CPAREN, EOL}; struct node { Type type; int data; node *lchild, *rchild; node(Type t, int d=0, node *lc=NULL, node *rc=NULL) { type=t; data=d; lchild=lc; rchild=rc; } }; node *root; node *create(char * &s); Type getToken (char * &s, int &value); int result (node *t); public: calc (char *s) { root=create(s); } int result() { if (root==NULL) return 0; return result(root); } }; calc::node *calc::create(char * &s) { node *p, *root=NULL; Type returnType,flag=DATA; int value; while (*s) { flag=returnType; returnType=getToken(s,value); switch (returnType) { case DATA: case OPAREN: if (returnType == DATA) p=new node(DATA,value); else p=create(s); if (root==NULL) root=p; else if (root->rchild==NULL) root->rchild=p; else root->rchild->rchild=p; break; case CPAREN: case EOL: return root; case ADD: case SUB: root=new node(returnType,0,root); break; case MULTI: case DIV: if (root->type==DATA || root->type==MULTI || root->type==DIV || flag==OPAREN) root=new node(returnType,0,root); else root->rchild=new node(returnType,0,root->rchild); } } return root; } calc::Type calc::getToken(char *&s, int &data) { char type; while (*s==' ') ++s; if (*s>='0' && *s<='9') { data=0; while (*s>='0' && *s<='9') {data=data*10+ *s-'0'; ++s;} return DATA; } if (*s == '\0') return EOL; type =*s; ++s; switch(type) { case '+':return ADD; case '-':return SUB; case '*':return MULTI; case '/':return DIV; case '(':return OPAREN; case ')':return CPAREN; default: return EOL; } } int calc::result(node *t) { int num1,num2; if (t->type == DATA) return t->data; num1=result(t->lchild); num2=result(t->rchild); switch(t->type) { case ADD:t->data=num1+num2;break; case SUB:t->data=num1-num2;break; case MULTI: t->data=num1*num2;break; case DIV:t->data=num1/num2;break; } return t->data; } int main() { char expression[256]; cin>>expression; calc exp(expression); cout<<exp.result()<<endl; return 0; } |
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