【数据结构与算法基础】栈及其应用后缀、中缀表达式 / Stack and postfix/infix expression

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/********************************************************************File: ListStack.hAuthor: blackboy, [e-mail]: 栈ADT，链表实现Created: 2011-03-31Modified: 2011-03-31 09:02*********************************************************************/#ifndef __LIST_STACK_H__#define __LIST_STACK_H__typedef int ElementType;struct _Node;typedef struct _Node Node;typedef Node* PtrToNode;typedef PtrToNode Stack;struct _Node{ElementType Val;PtrToNode Next;};//////////////////////////////////////////////////////////////////////////Stack CreateStack();void DisposeStack(Stack);void MakeEmpty(Stack);void Push(ElementType, Stack);void Pop(Stack);ElementType Top(Stack);int IsEmpty(Stack);#endif 

 

 

#include <stdlib.h>#include "ListStack.h"Stack CreateStack(){Stack S = (Node*)malloc(sizeof(Node));S->Next = NULL;return S;}void DisposeStack(Stack S){MakeEmpty(S);free(S);S = NULL;}void MakeEmpty(Stack S){while(!IsEmpty(S))Pop(S);}void Push(ElementType X, Stack S){PtrToNode p;p = (Node*)malloc(sizeof(Node));p->Val = X;p->Next = S->Next;S->Next = p;}void Pop(Stack S){PtrToNode p;if(IsEmpty(S))return;p = S->Next;S->Next = S->Next->Next;free(p);p = NULL;}ElementType Top(Stack S){if(IsEmpty(S))return 0;return S->Next->Val;}int IsEmpty(Stack S){return S->Next == NULL;} 

 

 

 

 

/********************************************************************File: calc.cAuthor: blackboy, [e-mail]: 将中缀表达式转换为后缀表达式，并求出它的值。 只考虑1位数字（0-9）操作数，及+，*，（，）4个操作符Created: 2011-04-01Modified: 2011-04-01 15:37*********************************************************************/#include <stdlib.h>#include <stdio.h>#include <string.h>#include <ctype.h>#include "ListStack.h"// Stack中元素类型为int#define MAX_INPUT 100void InfixToPostfix(char*);// 将中缀表达式（将标准的算术表达式）转换为后缀表达式int CalcPostfix(const char*);// 计算后缀表达式void PrintStack(Stack);// 将栈内容打印到标准输出int main(){char input[MAX_INPUT] = {0};//char input[] = "a+b*c+(d*e+f)*g";//char input[] = "2+3*2+(5*3+7)*2"; // 52printf("input infix expression(MAX: %d):/n", MAX_INPUT);gets(input);printf("infix: %s/n", input);InfixToPostfix(input);printf("postfix: %s/n", input);printf("result: %d/n", CalcPostfix(input));system("PAUSE");return 0;}int CalcPostfix(const char* input){Stack S;int i, a, b;char tmp;S = CreateStack();for(i=0; i<(int)strlen(input); ++i){if( isdigit(input[i]) ){tmp = input[i];Push(atoi(&tmp), S);}else{a = Top(S);Pop(S);b = Top(S); Pop(S);if(input[i] == '+')Push(a+b, S);else if(input[i] == '*')Push(a*b, S);}//PrintStack(S);}i = Top(S);DisposeStack(S);return i;}void InfixToPostfix(char* input){char* tmp = (char*)calloc(strlen(input) + 1, sizeof(char));Stack S;int i, j;S = CreateStack();j = 0;for(i=0; i<(int)strlen(input); ++i){if( isdigit(input[i]) ){tmp[j++] = input[i];}else if( input[i] == '+' ){while(!IsEmpty(S)){if(Top(S) == '+' || Top(S) == '*'){tmp[j++] = Top(S);Pop(S);}elsebreak;}Push(input[i], S);}else if( input[i] == '*' ){while(!IsEmpty(S)){if(Top(S) == '*'){tmp[j++] = Top(S);Pop(S);}else break;}Push(input[i], S);}else if( input[i] == '(' ){Push(input[i], S);}else if( input[i] == ')' ){while(Top(S) != '('){tmp[j++] = Top(S);Pop(S);}Pop(S);}}while(!IsEmpty(S)){tmp[j++] = Top(S);Pop(S);}DisposeStack(S);strcpy(input, tmp);}void PrintStack(Stack S){PtrToNode p = S->Next;while(p != NULL){printf("%d ", p->Val);p = p->Next;}printf("/n");}