Problem p01542 (C++) — buggy submission, verdict: Runtime Error

#include <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
// #define LOG(...)
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define RSORT(c) sort((c).rbegin(), (c).rend())
#define CLR(a) memset((a), 0, sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};

struct UnionFind {
  vector<int> v;
  UnionFind(int n) : v(n) {
    for (int i = 0; i < n; i++)
      v[i] = i;
  }
  int find(int x) { return v[x] == x ? x : v[x] = find(v[x]); }
  void unite(int x, int y) { v[find(x)] = find(y); }
};

int expr(string &s, int &num);
int term(string &s, int &num);
int factor(string &s, int &num);
int number(string &s, int &num);
int expr(string &s, int &num) {
  int val = term(s, num);
  if (val == -1)
    return -1;
  while (s[num] == '+' || s[num] == '-') {
    bool op = s[num] == '+';
    num++;
    int val2 = term(s, num);
    if (val2 == -1)
      return -1;
    if (op)
      val += val2;
    else
      val -= val2;

    if (val >= 1024)
      return -1;
    if (val < 0)
      return -1;
  }
  return val;
}
int term(string &s, int &num) {
  int val = factor(s, num);
  if (val == -1)
    return -1;
  while (s[num] == '*') {
    num++;
    int val2 = factor(s, num);
    if (val2 == -1)
      return -1;
    val *= val2;
    if (val >= 1024)
      return -1;
  }
  return val;
}
int factor(string &s, int &num) {
  if (isdigit(s[num]))
    return number(s, num);
  if (s[num] != '(')
    return -1;
  num++;
  int a = num;
  int ret = expr(s, num);
  if (s[num] != ')')
    return -1;
  num++;
  return ret;
}
int number(string &s, int &num) {
  int n = s[num++] - '0';
  while (isdigit(s[num])) {
    n = n * 2 + s[num++] - '0';
    if (n >= 1024)
      return -1;
  }
  return n;
}

int ma = -1;
void dfs(string s) {
  int a = s.find('.');
  if (a != string::npos) {
    string s2 = s;
    s2[a] = '+';
    dfs(s2);
    s2[a] = '-';
    dfs(s2);
    s2[a] = '*';
    dfs(s2);
    s2[a] = '0';
    dfs(s2);
    s2[a] = '1';
    dfs(s2);
    s2[a] = '(';
    dfs(s2);
    s2[a] = ')';
    dfs(s2);
  } else {
    int num = 0;
    stack<char> sc;
    REP(i, s.length()) {
      if (s[i] == '(')
        sc.push('(');
      if (s[i] == ')') {
        if (sc.empty())
          return;
        if (sc.top() == '(')
          return;
        else {
          do {
            sc.pop();
            if (sc.empty())
              return;
          } while (sc.top() != '(');
          sc.pop();
        }
      }
      if (s[i] == '+' || s[i] == '-' || s[i] == '*')
        sc.push('0');
    }
    int ans = -1;
    if (sc.empty() || sc.top() == '0') {
      ans = expr(s, num);
      if (s.length() == num) {
        ma = max(ma, ans);
        // cout << s << ' ' << ans << endl;
      }
    }
  }
}
int main() {
  string s;
  cin >> s;
  dfs(s);
  cout << ma << endl;
}

Error: -11

Fixed submission:

#include <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
// #define LOG(...)
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define RSORT(c) sort((c).rbegin(), (c).rend())
#define CLR(a) memset((a), 0, sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};

struct UnionFind {
  vector<int> v;
  UnionFind(int n) : v(n) {
    for (int i = 0; i < n; i++)
      v[i] = i;
  }
  int find(int x) { return v[x] == x ? x : v[x] = find(v[x]); }
  void unite(int x, int y) { v[find(x)] = find(y); }
};

int expr(string &s, int &num);
int term(string &s, int &num);
int factor(string &s, int &num);
int number(string &s, int &num);
int expr(string &s, int &num) {
  int val = term(s, num);
  if (val == -1)
    return -1;
  while (s[num] == '+' || s[num] == '-') {
    bool op = s[num] == '+';
    num++;
    int val2 = term(s, num);
    if (val2 == -1)
      return -1;
    if (op)
      val += val2;
    else
      val -= val2;
    if (val >= 1024)
      return -1;
    if (val < 0)
      return -1;
  }
  return val;
}
int term(string &s, int &num) {
  int val = factor(s, num);
  if (val == -1)
    return -1;
  while (s[num] == '*') {
    num++;
    int val2 = factor(s, num);
    if (val2 == -1)
      return -1;
    val *= val2;
    if (val >= 1024)
      return -1;
  }
  return val;
}
int factor(string &s, int &num) {
  if (isdigit(s[num]))
    return number(s, num);
  if (s[num] != '(')
    return -1;
  num++;
  int a = num;
  int ret = expr(s, num);
  if (s[num] != ')')
    return -1;
  num++;
  return ret;
}
int number(string &s, int &num) {
  int n = s[num++] - '0';
  while (isdigit(s[num]))
    n = n * 2 + s[num++] - '0';
  return n;
}

int ma = -1;
void dfs(string s) {
  int a = s.find('.');
  if (a != string::npos) {
    string s2 = s;
    s2[a] = '+';
    dfs(s2);
    s2[a] = '-';
    dfs(s2);
    s2[a] = '*';
    dfs(s2);
    s2[a] = '0';
    dfs(s2);
    s2[a] = '1';
    dfs(s2);
    s2[a] = '(';
    dfs(s2);
    s2[a] = ')';
    dfs(s2);
  } else {
    int num = 0;
    stack<char> sc;
    REP(i, s.length()) {
      if (s[i] == '(')
        sc.push('(');
      if (s[i] == ')') {
        if (sc.empty())
          return;
        if (sc.top() == '(')
          return;
        else {
          do {
            sc.pop();
            if (sc.empty())
              return;
          } while (sc.top() != '(');
          sc.pop();
        }
      }
      if (s[i] == '+' || s[i] == '-' || s[i] == '*')
        sc.push('0');
    }
    int ans = -1;
    if (sc.top() == '0') {
      ans = expr(s, num);
      ma = max(ma, ans);
    }
    // cout << s << ' ' << ans << endl;
  }
}
int main() {
  string s;
  cin >> s;
  dfs(s);
  cout << ma << endl;
}