简单计算器的设计与实现

#include<stdio.h> #include<stdlib.h> #define TRUE 1 #define FALSE 0 #define MAXNUM 100 typedef int DataType; struct SeqStack { DataType s[MAXNUM]; int t; }; typedef struct SeqStack *PSeqStack; PSeqStack createEmptyStack_seq() { PSeqStack pastack; pastack=(PSeqStack)malloc(sizeof(struct SeqStack)); if (pastack==NULL) { printf("超出空间!!\n"); } else { pastack->t=-1; } return pastack; } int isEmptyStack_seq(PSeqStack pastack) { return pastack->t==-1; } void push_seq(PSeqStack pastack, DataType x) { if (pastack->t >= MAXNUM - 1) printf("溢出!\n"); else { pastack->t = pastack->t+1; pastack->s[pastack->t]=x; } } void pop_seq(PSeqStack pastack) { if (pastack->t==-1) { printf("未溢出!\n"); } else { pastack->t = pastack->t-1; } } DataType top_seq(PSeqStack pastack) { return pastack->s[pastack->t]; } int infixtoSuffix(const char* infix, char* suffix) { /*将中缀表达式转换为后缀表达式，顺利转换返回true，若转换过程中发现中缀表达式非法则返回false*/ int state_int = FALSE; /*state_int记录状态，等于true表示刚读入的是数字字符，等于false表示刚读入的不是数字字符， 设置这个变量是为了在每输出一个整数后输出一个空格，以免连续输出的两个整数混在一起。*/ char c, c2; PSeqStack ps = createEmptyStack_seq(); /*运算符栈*/ int i, j = 0; if(infix[0]=='\0') { return FALSE; /*不允许出现空表达式*/ } for(i=0; infix[i]!='\0';i++) { c=infix[i]; switch(c) { case ' ': case '\t': case '\n': if(state_int== TRUE) { suffix[j++]=' ';/*状态从true转换为false时输出一个空格*/ } state_int= FALSE; break; /*遇到空格或制表符忽略*/ case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': case '.': state_int =TRUE; suffix[j++]=c; /*遇到数字输出*/ break; case '(': if(state_int==TRUE) { suffix[j++]=' ';/*状态从true转换为false时输出一个空格*/ } state_int=FALSE; push_seq(ps, c); /*遇到左括号，入栈*/ break; case ')': if(state_int== TRUE) { suffix[j++]=' ';/*状态从true转换为false时输出一个空格*/ } state_int=FALSE; c2 = ')'; while(!isEmptyStack_seq(ps)) { c2=top_seq(ps);/*取栈顶*/ pop_seq(ps); /*出栈*/ if(c2 =='(') { break; } suffix[j++]=c2; } if(c2 !='(') { free(ps); suffix[j++]='\0'; return FALSE; } break; case '+': case '-': if(state_int == TRUE) { suffix[j++] = ' '; } state_int = FALSE; while(!isEmptyStack_seq(ps)) { c2 = top_seq(ps); if(c2 =='+'|| c2 =='-'|| c2 == '*' || c2 == '/') { pop_seq(ps); suffix[j++] = c2; } else if(c2=='(') { break; } } push_seq(ps, c); break; case '*': case '/': if(state_int==TRUE) { suffix[j++] = ' '; } state_int = FALSE; while(!isEmptyStack_seq(ps)) { c2 = top_seq(ps); if(c2 == '*' || c2 == '/') { pop_seq(ps); suffix[j++] = c2; } else if(c2=='+'||c2=='-'||c2=='(') { break; } } push_seq(ps, c); break; default: free(ps); suffix[j++] = '\0'; return FALSE; } } if(state_int == TRUE) { suffix[j++] = ' '; } while(!isEmptyStack_seq(ps)) { c2 = top_seq(ps); pop_seq(ps); if(c2 == '(') { free(ps); suffix[j++] = '\0'; return FALSE; } suffix[j++] = c2; } free(ps); suffix[j++] = '\0'; return TRUE; } int calculateSuffix(const char * suffix, int * presult) { int state_int = FALSE; PSeqStack ps = createEmptyStack_seq(); int num = 0, num1, num2; int i; char c; for(i = 0; suffix[i] != '\0'; i++) { c = suffix[i]; switch(c) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': case '.': if(state_int == TRUE) { num = num * 10 + c - '0'; } else { num = c - '0'; } state_int = TRUE; break; case ' ': case'\t': case '\n': if (state_int == TRUE) { push_seq(ps, num); state_int = FALSE; } break; case '+': case '-': case '*': case '/': if(state_int == TRUE) { push_seq(ps, num); state_int = FALSE; } if(isEmptyStack_seq(ps)) { free(ps); return FALSE; } num2 = top_seq(ps); pop_seq(ps); if(isEmptyStack_seq(ps)) { free(ps); return FALSE; } num1 = top_seq(ps); pop_seq(ps); if(c == '+') { push_seq(ps, num1 + num2); } if(c == '-') { push_seq(ps, num1 - num2); } if(c == '*') { push_seq(ps, num1 * num2); } if(c == '/') { push_seq(ps, num1 / num2); } break; default: free(ps); return FALSE; } } *presult = top_seq(ps); pop_seq(ps); if(!isEmptyStack_seq(ps)) { free(ps); return FALSE; } free(ps); return TRUE; } void getline(char* line, int limit) { char c; int i=0; while(i<limit-1&&(c = getchar())!=EOF&&c!='\n') { line[i++]=c; } line[i]='\0'; } int main() { char c, infix[MAXNUM], suffix[MAXNUM]; int result; int flag = TRUE; while(flag == TRUE) { printf("========================================\n"); printf("==== 表达式计算器的设计与实现 ====\n"); printf("==== 计本051 刘璐 051841015 ====\n"); printf("========================================\n"); printf("请输入一个表达式!\n"); printf("输入:"); getline(infix, MAXNUM); if(infixtoSuffix(infix, suffix) == TRUE) { printf("后缀表达式为:%s\n", suffix); } else { printf("无效后缀!\n"); printf("\n是否继续? (y/n)"); scanf("%c", &c); if(c == 'n' || c == 'N') { flag = FALSE; } while(getchar() != '\n'); { printf("\n"); } continue; } if(calculateSuffix(suffix, &result) == TRUE) { printf("结果为:%d\n", result); } else { printf("输入有误!\n"); } printf("\n是否继续? (y/n)"); scanf("%c", &c); if(c == 'n' || c == 'N') { flag = FALSE; } while(getchar() != '\n'); { printf("\n"); } } }