Data Structure Stack: Infix to Postfix
http://geeksquiz.com/stack-set-2-infix-to-postfix/
1 #include <iostream> 2 #include <vector> 3 #include <algorithm> 4 #include <queue> 5 #include <stack> 6 #include <string> 7 #include <fstream> 8 #include <map> 9 #include <set> 10 using namespace std; 11 12 bool isoprand(char x) { 13 return x >= 'A' && x <= 'Z' || x >= 'a' && x <= 'z'; 14 } 15 16 int prec(char x) { 17 if (x == '+' || x == '-') return 1; 18 if (x == '*' || x == '/') return 2; 19 if (x == '^') return 3; 20 return -1; 21 } 22 23 int infixtopostfix(string s) { 24 string ans; 25 stack<char> T; 26 for (int i = 0; i < s.size(); i++) { 27 if (isoprand(s[i])) ans += s[i]; 28 else if (s[i] == '(') T.push(s[i]); 29 else if (s[i] == ')') { 30 while (!T.empty() && T.top() != '(') { 31 ans += T.top(); 32 T.pop(); 33 } 34 if (!T.empty() && T.top() != '(') return -1; 35 T.pop(); 36 } 37 else { 38 while (!T.empty() && prec(s[i]) <= prec(T.top())) { 39 ans += T.top(); 40 T.pop(); 41 } 42 T.push(s[i]); 43 } 44 } 45 while (!T.empty()) { 46 ans += T.top(); 47 T.pop(); 48 } 49 cout << ans << endl; 50 } 51 52 int main() { 53 string s = "a+b*(c^d-e)^(f+g*h)-i"; 54 infixtopostfix(s); 55 return 0; 56 }
