#define MAX 20
typedef struct stackNum {
double m_data[MAX]; int p_now; }stackNum;
typedef struct stackOper {
int m_data[MAX]; int p_now; }stackOper;
void initstack(); /*初始化堆栈*/
int Make_str(); /*语法检查并计算*/ int push_num(double num); /*将操作数压入堆栈*/ int procede(int operate); /*处理操作码*/
int change_opnd(int operate); /*将字符型操作码转换成优先级*/ int push_opnd(int operate); /*将操作码压入堆栈*/ int pop_opnd(); /*将操作码弹出堆栈*/
double caculate(int cur_opnd); /*简单计算+，-，*，/*/ double pop_num(); /*弹出操作数*/
void error(int number); int seekOper();
int isDigit(char ch); int isOper(char oper);
stackNum StackOfNum; stackOper StackOfOper; char buf[MAX*5]; double number; int HaveResult;
int main() {
initstack(); gets(buf); if(Make_str()) {
printf(\"结果为\%lf\\n\ }
return 0; }
void initstack() {
StackOfNum.p_now = 0; StackOfOper.p_now = 0; }
int Make_str() {
int process = 0; int numberLength; double temp;
char NumberTemp[20]; int size = strlen(buf); HaveResult = 1;
while(process < size) {
if(isDigit(buf[process])) {
numberLength = 1;
while(isDigit(buf[process + numberLength])) {
++numberLength; }
strncpy(NumberTemp,buf+process,numberLength); NumberTemp[numberLength] = '\\0'; temp = atof(NumberTemp); push_num(temp);
process += numberLength; }
else if(isOper(buf[process])) {
procede(buf[process++]); } else {
error(1); return 0; } }
while(StackOfOper.p_now != 0 && HaveResult) {
push_num(caculate(pop_opnd())); }
number = pop_num(); return HaveResult; }
void error(int number) {
if(1 == number) {
printf(\"有非法字符\\n\"); }
else if(2 == number) {
printf(\"表达式不合法\"); }
else if(3 == number) {
printf(\"表达式过长\"); }
HaveResult = 0; }
int seekOper() {
if( 0 == StackOfOper.p_now ) {
error(2); return 0; }
return StackOfOper.m_data[StackOfOper.p_now - 1]; }
int isDigit(char ch) {
if('0' <= ch && ch <= '9') {
return 1; }
if('.' == ch) {
return 1; }
return 0; }
int isOper(char oper) {
if('+' == oper || '-' == oper || '*' == oper || '/' == oper) {
return 1; }
return 0; }
int push_num(double num) {
if(StackOfNum.p_now == MAX) {
error(3); return 0; }
StackOfNum.m_data[StackOfNum.p_now++] = num; return 1; }
int push_opnd(int operate) {
if(StackOfOper.p_now == MAX) {
error(3); return 0; }
StackOfOper.m_data[StackOfOper.p_now++] = operate; return 1; }
int pop_opnd() {
if(StackOfOper.p_now == 0) {
error(2); return 0; }
return StackOfOper.m_data[--StackOfOper.p_now]; }
double pop_num()
{
if(StackOfNum.p_now == 0) {
error(2); return 0; }
return StackOfNum.m_data[--StackOfNum.p_now]; }
double caculate(int cur_opnd) {
double left,right; right = pop_num(); left = pop_num(); switch(cur_opnd) {
case '+': {
return left + right; } case '-': {
return left - right; } case '*': {
return left * right; } case '/': {
return left / right; } }
return 0; }
int procede(int operate) {
if(StackOfOper.p_now == 0) {
push_opnd(operate); return 1; } else {
if(change_opnd(seekOper()) > change_opnd(operate)) {
push_num(caculate(pop_opnd())); }
push_opnd(operate); return 1; }
return 0; }
int change_opnd(int operate) {
if('+' == operate || '-' == operate) {
return 1; }
else if('*' == operate || '/' == operate) {
return 2; }
return 0; }
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