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  1. #include <iostream>
  2. #include <string>
  3. #include <vector>
  4.  
  5. using namespace std;
  6.  
  7. struct Term {
  8.     long long c;
  9.     string v;
  10. };
  11.  
  12. Term parseTerm(const string& s) {
  13.     long long c = 0;
  14.     int sign = 1;
  15.     size_t i = 0;
  16.     if (i < s.size() && s[i] == '+') i++;
  17.     else if (i < s.size() && s[i] == '-') { sign = -1; i++; }
  18.  
  19.     bool has_digit = false;
  20.     while(i < s.size() && isdigit(s[i])) {
  21.         c = c * 10 + (s[i] - '0');
  22.         has_digit = true;
  23.         i++;
  24.     }
  25.     if (!has_digit) c = 1;
  26.     c *= sign;
  27.     return {c, s.substr(i)};
  28. }
  29.  
  30. string formatSq(const Term& t, bool isFirst) {
  31.     long long c2 = t.c * t.c;
  32.     if (c2 == 0) return "";
  33.     string res = "";
  34.     if (c2 > 0 && !isFirst) res += "+";
  35.  
  36.     if (t.v.empty()) {
  37.         res += to_string(c2);
  38.     } else {
  39.         if (c2 != 1) res += to_string(c2);
  40.         res += t.v + "^2";
  41.     }
  42.     return res;
  43. }
  44.  
  45. string formatCross(const Term& t1, const Term& t2, bool isFirst) {
  46.     long long c = 2 * t1.c * t2.c;
  47.     if (c == 0) return "";
  48.     string res = "";
  49.     if (c > 0 && !isFirst) res += "+";
  50.     else if (c < 0) { res += "-"; c = -c; }
  51.  
  52.     if (t1.v.empty() && t2.v.empty()) {
  53.         res += to_string(c);
  54.     } else {
  55.         if (c != 1) res += to_string(c);
  56.         res += t1.v + t2.v;
  57.     }
  58.     return res;
  59. }
  60.  
  61. int main() {
  62.     ios_base::sync_with_stdio(false);
  63.     cin.tie(NULL);
  64.     string line;
  65.     while (getline(cin, line)) {
  66.         string full = "";
  67.         for (char c : line) {
  68.             if (c != ' ' && c != '\t' && c != '\r') full += c;
  69.         }
  70.         if (full.empty()) continue;
  71.  
  72.         size_t p1 = full.find('(');
  73.         size_t p2 = full.find(')');
  74.         if (p1 == string::npos || p2 == string::npos || p2 < p1) {
  75.             p1 = -1;
  76.             p2 = full.length();
  77.             size_t p_sq = full.find("^2");
  78.             if(p_sq != string::npos) p2 = p_sq;
  79.         }
  80.  
  81.         string in = full.substr(p1 + 1, p2 - p1 - 1);
  82.         vector<Term> T;
  83.         string current = "";
  84.         for(char ch : in) {
  85.             if(ch == '+' || ch == '-') {
  86.                 if(!current.empty()) {
  87.                     T.push_back(parseTerm(current));
  88.                 }
  89.                 current = (ch == '-') ? "-" : "";
  90.             } else {
  91.                 current += ch;
  92.             }
  93.         }
  94.         if(!current.empty()) {
  95.             T.push_back(parseTerm(current));
  96.         }
  97.  
  98.         if (T.empty()) continue;
  99.  
  100.         string ans = "";
  101.         if (T.size() == 2) {
  102.             ans += formatSq(T[0], true);
  103.             ans += formatCross(T[0], T[1], false);
  104.             ans += formatSq(T[1], false);
  105.         } else {
  106.             bool isFirst = true;
  107.             for (size_t i = 0; i < T.size(); i++) {
  108.                 ans += formatSq(T[i], isFirst);
  109.                 isFirst = false;
  110.             }
  111.             for (size_t i = 0; i < T.size(); i++) {
  112.                 for (size_t j = i + 1; j < T.size(); j++) {
  113.                     ans += formatCross(T[i], T[j], isFirst);
  114.                     isFirst = false;
  115.                 }
  116.             }
  117.         }
  118.  
  119.         if (full.find("ex:") == 0) {
  120.             cout << "res:" << ans << "\n";
  121.         } else {
  122.             cout << ans << "\n";
  123.         }
  124.     }
  125.     return 0;
  126. }
Success #stdin #stdout 0.01s 5324KB
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https://ideone.com/d8Y1AC
(a+b)^3
language:
C++14 (gcc 8.3)
created:
16 hours ago
visibility:
public

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