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  1. #include <iostream>
  2. #include <stack>
  3. #include <string>
  4. using namespace std;
  5.  
  6. int main() {
  7.     int t;
  8.     cin >> t;
  9.  
  10.     while (t--) {
  11.     	int n;
  12.     	cin >> n;
  13.     	cin.ignore();
  14.         string expr;
  15.         cin >> expr;
  16.  
  17.         stack<long long> st;
  18.         bool valid = true;
  19.  
  20.         for (int i = expr.size() - 1; i >= 0; --i) {
  21.             char c = expr[i];
  22.             if (c >= '0' && c <= '9') {
  23.                 st.push(c - '0');  // convert char to number
  24.             } else if (c == '+' || c == '-' || c == '*' || c == '/') {
  25.                 if (st.size() < 2) {
  26.                     valid = false;
  27.                     break;
  28.                 }
  29.                 long long a = st.top(); st.pop();
  30.                 long long b = st.top(); st.pop();
  31.                 if (c == '+') st.push(a + b);
  32.                 else if (c == '-') st.push(a - b);
  33.                 else if (c == '*') st.push(a * b);
  34.                 else if (c == '/') {
  35.                     if (b == 0) {
  36.                         valid = false;
  37.                         break;
  38.                     }
  39.                     st.push(a / b);
  40.                 }
  41.             } else {
  42.                 valid = false;
  43.                 break;
  44.             }
  45.         }
  46.  
  47.         if (valid && st.size() == 1) {
  48.             cout << st.top() << endl;
  49.         } 
  50.  
  51.     }
  52.  
  53.     return 0;
  54. }
Success #stdin #stdout 0s 5316KB
comments (?)
stdin
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2
7
+ * - 5 4 100 20
3
- 4 7
stdout
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Standard output is empty
https://ideone.com/P1pTxS
language:
C++ (gcc 8.3)
created:
3 days ago
visibility:
public

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