#include<bits/stdc++.h> using namespace std; vector<pair<bool, int> > v; string s; int l, p; void popraw(){ while(v[l].second == 0) l++; while(v[p].second == 0) p--; } int main(){ cin >> s; //a->0, b->1 v.push_back({s[0] == 'b', 1}); for(int i = 1 ; i < s.size() ; i++){ int it = v.size() - 1; int x = v[it].second; if(s[i] == s[i-1]){ v[it] = {v[it].first, x+1}; } else{ v.push_back({!v[it].first, 1}); } } long long wynik = 0; p = v.size() - 1; l = 0; while(true){ while(v[l].first == v[p].first){ if(l == p){ cout << wynik; return 0; } int mini = min(v[l].second, v[p].second); v[l].second -= mini; v[p].second -= mini; popraw(); } if(v[l].second <= v[p].second){ wynik += v[l].second; v[p].second--; v[l+1].second--; if(v[l+1].second == -1){ cout << -1; return 0; } if(v[l+1].second == 0){ if(l + 2 > p){ cout << wynik; return 0; } v[l + 2].second += v[l].second; v[l].second = 0; l += 2; } while (v[p].second == 0) p--; } else if(v[l].second > v[p].second){ wynik += v[p].second; v[l].second--; v[p-1].second--; if(v[p-1].second == -1){ cout << -1; return 0; } if(v[p-1].second == 0){ if(p - 2 < l){ cout << wynik; return 0; } v[p-2].second += v[p].second; v[p].second = 0; p -= 2; } while(v[l].second == 0) l++; } } }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 | #include<bits/stdc++.h> using namespace std; vector<pair<bool, int> > v; string s; int l, p; void popraw(){ while(v[l].second == 0) l++; while(v[p].second == 0) p--; } int main(){ cin >> s; //a->0, b->1 v.push_back({s[0] == 'b', 1}); for(int i = 1 ; i < s.size() ; i++){ int it = v.size() - 1; int x = v[it].second; if(s[i] == s[i-1]){ v[it] = {v[it].first, x+1}; } else{ v.push_back({!v[it].first, 1}); } } long long wynik = 0; p = v.size() - 1; l = 0; while(true){ while(v[l].first == v[p].first){ if(l == p){ cout << wynik; return 0; } int mini = min(v[l].second, v[p].second); v[l].second -= mini; v[p].second -= mini; popraw(); } if(v[l].second <= v[p].second){ wynik += v[l].second; v[p].second--; v[l+1].second--; if(v[l+1].second == -1){ cout << -1; return 0; } if(v[l+1].second == 0){ if(l + 2 > p){ cout << wynik; return 0; } v[l + 2].second += v[l].second; v[l].second = 0; l += 2; } while (v[p].second == 0) p--; } else if(v[l].second > v[p].second){ wynik += v[p].second; v[l].second--; v[p-1].second--; if(v[p-1].second == -1){ cout << -1; return 0; } if(v[p-1].second == 0){ if(p - 2 < l){ cout << wynik; return 0; } v[p-2].second += v[p].second; v[p].second = 0; p -= 2; } while(v[l].second == 0) l++; } } } |