表达式计算（双栈实现）

问题：计算下列表达式
　　1+2*3-4-（2-（-1））*2+4/2
计算中包含+，-，*，/，（，），数字，负号（-）


 1 #include <iostream>
 2 #include <stack>
 3 
 4 using namespace std;
 5 
 6 bool isOp(string &val, int pos) {
 7     if (val[pos] == '-') {
 8         if (pos == 0 || isOp(val, pos-1)) {
 9             return false;
10         }
11     }
12     char c = val[pos];
13     return (c == '+' || c == '-' || c == '*' || c == '/' || c == '(' || c == ')');
14 }
15 
16 int getPriority(char c) {
17     if (c == '(' || c == ')')
18         return 0;
19     else if (c == '+' || c == '-') 
20         return 1;   
21     else if (c == '*' || c == '/')
22         return 2;
23     return 0;
24 }
25 
26 int getResult(int a, int b, char op) {
27     if (op == '+')
28         return a + b;
29     else if (op == '-')
30         return a - b;
31     else if (op == '*')
32         return a * b;
33     else if (op == '/')
34         return a / b;
35     return 0;
36 }
37 
38 void calculate(stack<int> &data, stack<char> &op) {
39     char ch = op.top();
40     int behind = data.top();
41     data.pop();
42     int before = data.top();
43     data.pop();
44     data.push(getResult(before, behind, ch));
45     op.pop();
46 }
47 
48 int main() {
49     string val;
50     cin >> val;
51     int result = 0;
52     stack<int> data;
53     stack<char> op;
54     string tmp = "";
55     for (int i = 0; i < val.length(); ++i) {
56         if (isOp(val, i) ) {
57             if (!tmp.empty()) {
58                 data.push(atoi(tmp.c_str()));
59                 tmp.clear();
60             }
61             if (op.empty() || val[i] == '(') {
62                 op.push(val[i]);
63             } else {
64                 bool bKuoHao = false;
65                 while (!op.empty() && getPriority(op.top()) >= getPriority(val[i])) {
66                     if (val[i] == ')') {
67                         while(!op.empty() && op.top() != '(') {
68                             calculate(data, op);
69                         }
70                         op.pop();
71                         bKuoHao = true;
72                         break;
73                     } else {
74                         calculate(data, op);
75                     }
76                 }
77                 if (!bKuoHao)
78                     op.push(val[i]);
79             }
80         } else {
81             tmp += val[i];
82             if (i == val.length() - 1) {
83                 data.push(atoi(tmp.c_str()));
84                 tmp.clear();
85             }
86         }
87     }
88     while(!op.empty()) {
89         calculate(data, op);
90     }
91     cout << data.top() << endl;
92 
93     return 0;
94 }

上面的不支持浮点数的计算，所以这里再调整一下数据类型

 1 #include <iostream>
 2 #include <stack>
 3 
 4 using namespace std;
 5 
 6 bool isOp(string &val, int pos) {
 7     if (val[pos] == '-') {
 8         if (pos == 0 || isOp(val, pos-1)) {
 9             return false;
10         }
11     }
12     char c = val[pos];
13     return (c == '+' || c == '-' || c == '*' || c == '/' || c == '(' || c == ')');
14 }
15 
16 int getPriority(char c) {
17     if (c == '(' || c == ')')
18         return 0;
19     else if (c == '+' || c == '-') 
20         return 1;   
21     else if (c == '*' || c == '/')
22         return 2;
23     return 0;
24 }
25 
26 double getResult(double a, double b, char op) {
27     if (op == '+')
28         return a + b;
29     else if (op == '-')
30         return a - b;
31     else if (op == '*')
32         return a * b;
33     else if (op == '/')
34         return a / b;
35     return 0;
36 }
37 
38 void calculate(stack<double> &data, stack<char> &op) {
39     char ch = op.top();
40     double behind = data.top();
41     data.pop();
42     double before = data.top();
43     data.pop();
44     data.push(getResult(before, behind, ch));
45     op.pop();
46 }
47 
48 int main() {
49     string val;
50     cin >> val;
51     int result = 0;
52     stack<double> data;
53     stack<char> op;
54     string tmp = "";
55     for (int i = 0; i < val.length(); ++i) {
56         if (isOp(val, i) ) {
57             if (!tmp.empty()) {
58                 data.push(atof(tmp.c_str()));
59                 tmp.clear();
60             }
61             if (op.empty() || val[i] == '(') {
62                 op.push(val[i]);
63             } else {
64                 bool bKuoHao = false;
65                 while (!op.empty() && getPriority(op.top()) >= getPriority(val[i])) {
66                     if (val[i] == ')') {
67                         while(!op.empty() && op.top() != '(') {
68                             calculate(data, op);
69                         }
70                         op.pop();
71                         bKuoHao = true;
72                         break;
73                     } else {
74                         calculate(data, op);
75                     }
76                 }
77                 if (!bKuoHao)
78                     op.push(val[i]);
79             }
80         } else {
81             tmp += val[i];
82             if (i == val.length() - 1) {
83                 data.push(atof(tmp.c_str()));
84                 tmp.clear();
85             }
86         }
87     }
88     while(!op.empty()) {
89         calculate(data, op);
90     }
91     cout << data.top() << endl;
92 
93     return 0;
94 }

标签：return,val,int,双栈,else,计算,data,表达式,op
来源： https://www.cnblogs.com/zllwxm123/p/16408583.html