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  1. #include <iostream>
  2. #include <stack>
  3. #include <string>
  4. #include <sstream>
  5. #include <vector>
  6. using namespace std;
  7.  
  8. int main() {
  9.     int t;
  10.     cin >> t;
  11.     cin.ignore(); // skip newline after t
  12.  
  13.     while (t--) {
  14.         int n;
  15.         cin >> n;
  16.         cin.ignore(); // skip newline after n
  17.  
  18.         string line;
  19.         getline(cin, line); // read the full expression
  20.  
  21.         // Tokenize
  22.         vector<string> tokens;
  23.         stringstream ss(line);
  24.         string token;
  25.         while (ss >> token) {
  26.             tokens.push_back(token);
  27.         }
  28.  
  29.         if (tokens.size() != n) {
  30.             cout << "Invalid Expression" << endl;
  31.             continue;
  32.         }
  33.  
  34.         stack<long long> st;
  35.         bool valid = true;
  36.  
  37.         for (int i = tokens.size() - 1; i >= 0; --i) {
  38.             string tok = tokens[i];
  39.  
  40.             if (isdigit(tok[0]) || (tok[0] == '-' && tok.size() > 1)) {
  41.                 // valid number
  42.                 st.push(stoll(tok));
  43.             } else if (tok == "+" || tok == "-" || tok == "*" || tok == "/") {
  44.                 if (st.size() < 2) {
  45.                     valid = false;
  46.                     break;
  47.                 }
  48.                 long long a = st.top(); st.pop();
  49.                 long long b = st.top(); st.pop();
  50.  
  51.                 if (tok == "+") st.push(a + b);
  52.                 else if (tok == "-") st.push(a - b);
  53.                 else if (tok == "*") st.push(a * b);
  54.                 else if (tok == "/") {
  55.                     if (b == 0) {
  56.                         valid = false;
  57.                         break;
  58.                     }
  59.                     st.push(a / b);
  60.                 }
  61.             } else {
  62.                 valid = false;
  63.                 break;
  64.             }
  65.         }
  66.  
  67.         if (valid && st.size() == 1) {
  68.             cout << st.top() << endl;
  69.         } else {
  70.             cout << "Invalid Expression" << endl;
  71.         }
  72.     }
  73.  
  74.     return 0;
  75. }
  76.  
Success #stdin #stdout 0.01s 5312KB
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https://ideone.com/5fOgsl
language:
C++ (gcc 8.3)
created:
3 days ago
visibility:
public

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