Problem p02266 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cstdio>
#include <numeric>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

int main() {
  char ss[20010];
  scanf("%s", ss);
  const string s = ss;
  auto f = [&s](int start) {
    vector<pair<char, int>> st;
    vector<int> v;
    int depth = 0;
    int current = 0;
    for (size_t i = start; i < s.size(); ++i) {
      switch (s[i]) {
      case '\\\\':
        current += depth * 2 + 1;
        depth += 1;
        st.push_back(make_pair(s[i], i));
        break;
      case '_':
        current += depth * 2;
        break;
      case '/':
        depth -= 1;
        current += depth * 2 + 1;
        if (st.empty()) {
          depth = 0;
          current = 0;
        } else {
          st.pop_back();
          if (st.empty()) {
            v.push_back(current / 2);
            depth = 0;
            current = 0;
          }
        }
        break;
      }
      // printf("stacksize: %ld, depth: %d, current: %d\\n", st.size(),
      // depth,
      //       current);
    }
    if (st.empty()) {
      return make_pair(v, -2);
    } else {
      return make_pair(v, st[0].second);
    }
  };
  vector<int> v;
  int start = 0;
  do {
    auto r = f(start);
    v.insert(end(v), begin(r.first), end(r.first));
    start = r.second + 1;
    if (accumulate(begin(s) + start, end(s), true,
                   [](bool lhs, char rhs) { return lhs && rhs == '\\\\'; })) {
      // There is no valid area.
      break;
    }
  } while (start != -1);
  //    for (auto&& i : st) {
  //        printf("%c %d ", i.first, i.second);
  //    }
  // putchar('\\n');
  // putchar('\\n');
  printf("%d\\n", accumulate(begin(v), end(v), 0));
  if (v.size() == 0) {
    printf("%ld\\n", v.size());
  } else {
    printf("%ld ", v.size());
  }
  for (size_t i = 0; i < v.size(); ++i) {
    if (i != v.size() - 1) {
      printf("%d ", v[i]);
    } else {
      printf("%d\\n", v[i]);
    }
  }
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cstdio>
#include <numeric>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

int main() {
  char ss[20010];
  scanf("%s", ss);
  const string s = ss;
  auto f = [&s](int start) {
    vector<pair<char, int>> st;
    vector<int> v;
    int depth = 0;
    int current = 0;
    for (size_t i = start; i < s.size(); ++i) {
      switch (s[i]) {
      case '\\\\':
        current += depth * 2 + 1;
        depth += 1;
        st.push_back(make_pair(s[i], i));
        break;
      case '_':
        current += depth * 2;
        break;
      case '/':
        depth -= 1;
        current += depth * 2 + 1;
        if (st.empty()) {
          depth = 0;
          current = 0;
        } else {
          st.pop_back();
          if (st.empty()) {
            v.push_back(current / 2);
            depth = 0;
            current = 0;
          }
        }
        break;
      }
      // printf("stacksize: %ld, depth: %d, current: %d\\n", st.size(),
      // depth,
      //       current);
    }
    if (st.empty()) {
      return make_pair(v, -2);
    } else {
      return make_pair(v, st[0].second);
    }
  };
  vector<int> v;
  int start = 0;
  do {
    auto r = f(start);
    v.insert(end(v), begin(r.first), end(r.first));
    start = r.second + 1;
  } while (start != -1);
  //    for (auto&& i : st) {
  //        printf("%c %d ", i.first, i.second);
  //    }
  // putchar('\\n');
  // putchar('\\n');
  printf("%d\\n", accumulate(begin(v), end(v), 0));
  if (v.size() == 0) {
    printf("%ld\\n", v.size());
  } else {
    printf("%ld ", v.size());
  }
  for (size_t i = 0; i < v.size(); ++i) {
    if (i != v.size() - 1) {
      printf("%d ", v[i]);
    } else {
      printf("%d\\n", v[i]);
    }
  }
}