使用栈来实现含括号的四则运算，复杂的就是各种分支的判断，当时参考了很多前辈的代码，又自己敲了很久，得到一个最终版，在此记录一下，希望若干年后的自己看到时能够不忘初心。
#include<stdio.h>
#include<stdlib.h>
/*数据栈*/
struct shuju {
float data[100];
int top;
};
/*符号栈*/
struct fuhao {
char symbol[100];
int top;
};
void InitOperateNum(struct shuju *StackNum)
{
StackNum->top = -1;
}
void InitOperateSymbol(struct fuhao *StackSymbol)
{
StackSymbol->top = -1;
}
/*存入数据栈*/
void Inshuju(struct shuju *StackNum, int num)
{
StackNum->top ++;
StackNum->data[StackNum->top] = num;
}
/*存入符号栈*/
void Infuhao(struct fuhao *StackSymbol, char ch)
{
StackSymbol->top ++;
StackSymbol->symbol[StackSymbol->top] = ch;
}
/*读取数据栈*/
int Readshuju(struct shuju *StackNum)
{
return StackNum->data[StackNum->top];
}
/*读取符号栈*/
char Readfuhao(struct fuhao *StackSymbol)
{
return StackSymbol->symbol[StackSymbol->top];
}
/*从数据栈取出数据*/
int Putshuju(struct shuju *StackNum)
{
int x;
x = StackNum->data[StackNum->top];
StackNum->top --;
return x;
}
/*从符号栈取出符号*/
char Putfuhao(struct fuhao *StackSymbol)
{
char c;
c = StackSymbol->symbol[StackSymbol->top];
StackSymbol->top --;
return c;
}
/*符号优先级判断*/
int judge(char ch) {
if(ch == '(') {
return 1;
}
if(ch == '+' || ch == '-') {
return 2;
}
else if(ch == '*' || ch == '/') {
return 3;
}
else if(ch == ')') {
return 4;
}
}
/*四则运算*/
int Math(float v1, float v2, char c)
{
float sum;
switch(c) {
case '+' : {
sum = v1 + v2;
break;
}
case '-' : {
sum = v1 - v2;
break;
}
case '*' : {
sum = v1 * v2;
break;
}
case '/' : {
sum = v1 / v2;
break;
}
}
return sum;
}
void manu(){
printf("**********************************************************\n");
printf("\t算术运算菜单\n");
printf("1、加法运算\n");
printf("2、减法运算\n");
printf("3、乘法运算\n");
printf("4、除法运算\n");
printf("5、混合运算（无括号）\n");
printf("6、混合运算（有括号）\n");
printf("0、输入0退出程序\n");
printf("**********************************************************\n");
}
int main()
{
while(1){
manu();
printf("请输入表达式：");
struct shuju data;
struct fuhao symbol;
InitOperateNum(&data);
InitOperateSymbol(&symbol);
int i, t;
float v1, v2;
float sum;
char c;
i = t = 0;
sum =0;
char v[100] = {0};
char *str = (char *)malloc(sizeof(char)*200);
while((c = getchar()) != '\n') {
str[i] = c;
i ++;
}
str[i] = '\0';
for(i = 0; str[i] != '\0'; i ++) {
if(i == 0 && str[i] == '-') {
v[t++] = str[i];
}
else if(str[i] == '(' && str[i+1] == '-') {
i ++;
v[t++] = str[i++];
while(str[i] >= '0' && str[i] <= '9') {
v[t] = str[i];
t ++;
i ++;
}
Inshuju(&data, atoi(v));
while(t > 0) {
v[t] = 0;
t --;
}
if(str[i] != ')') {
i --;
Infuhao(&symbol, '(');
}
}
else if(str[i] >= '0' && str[i] <= '9') {
while(str[i] >= '0' && str[i] <= '9') {
v[t] = str[i];
t ++;
i ++;
}
Inshuju(&data, atoi(v));
while(t > 0) {
v[t] = 0;
t --;
}
i --;
}
else {
if(symbol.top == -1) { //如果符号栈没有元素，直接把符号放入符号栈
Infuhao(&symbol, str[i]);
}
else if(judge(str[i]) == 1) { //如果此符号是'('，直接放入符号栈
Infuhao(&symbol, str[i]);
}
else if(judge(str[i]) == 2) { //如果此符号是'+'或'-'，判断与栈顶符号是优先级
if(judge(Readfuhao(&symbol)) == 1) { //如果栈顶符号是'('，放入符号栈
Infuhao(&symbol, str[i]);
}
else if(judge(Readfuhao(&symbol)) == 2) { //如果栈顶符号是'+'或'-'，则出栈运算
while(symbol.top >= 0 && data.top >= 1) { //循环出栈
v2 = Putshuju(&data);
v1 = Putshuju(&data);
sum = Math(v1, v2, Putfuhao(&symbol));
Inshuju(&data, sum); //将运算结果压入数据栈
}
Infuhao(&symbol, str[i]); //新符号进栈
}
else if(judge(Readfuhao(&symbol)) == 3) { //如果栈顶符号是'*'或'/'，则进符号栈
while(symbol.top >= 0 && data.top >= 1) { //循环出栈
v2 = Putshuju(&data);
v1 = Putshuju(&data);
sum = Math(v1, v2, Putfuhao(&symbol));
Inshuju(&data, sum); //将运算结果压入数据栈
}
Infuhao(&symbol, str[i]); //新符号进栈
}
/*栈顶符号不可能是')'，故不做判断*/
}
else if(judge(str[i]) == 3) { //如果此符号是'*'或'/'，则判断与栈顶符号是优先级
if(judge(Readfuhao(&symbol)) == 1) { //如果栈顶符号是'('，放入符号栈
Infuhao(&symbol, str[i]);
}
else if(judge(Readfuhao(&symbol)) == 2) { //如果栈顶符号是'+'或'-'，则进符号栈
Infuhao(&symbol, str[i]); //新符号进栈
}
else if(judge(Readfuhao(&symbol)) == 3) { //如果栈顶符号是'*'或'/'，则出栈运算
while(symbol.top >= 0 && data.top >= 1) { //循环出栈
v2 = Putshuju(&data);
v1 = Putshuju(&data);
sum = Math(v1, v2, Putfuhao(&symbol));
Inshuju(&data, sum); //将运算结果压入数据栈
}
Infuhao(&symbol, str[i]); //新符号进栈
}
}
else if(judge(str[i]) == 4) { // 如果栈顶符号是')'，则出栈运算直到遇到'('
do { //循环出栈直到遇到'('
v2 = Putshuju(&data);
v1 = Putshuju(&data);
sum = Math(v1, v2, Putfuhao(&symbol));
Inshuju(&data, sum); //将运算结果压入数据栈
}while(judge(Readfuhao(&symbol)) != 1);
Putfuhao(&symbol); //括号内运算结束后使'('出栈
}
}
}
free(str); //释放内存空间
while(symbol.top != -1) {
v2 = Putshuju(&data);
v1 = Putshuju(&data);
sum = Math(v1, v2, Putfuhao(&symbol));
Inshuju(&data, sum);
}
printf("%.2f\n", data.data[0]);
}
return 0;
}