#include<bits/stdc++.h> using namespace std; // define #define execute cerr << " Time: " << fixed << setprecision(6) << (1.0 * clock() / CLOCKS_PER_SEC) << "s\n"; #define ll long long #define ii pair <int , int> #define iii pair <int , ii> #define se second #define fi first #define all(v) (v).begin() , (v).end() #define Unique(v) sort(all(v)) , v.resize(unique(all(v)) - v.begin()) #define bit(x,i) (((x) >> (i)) & 1LL) #define flip(x,i) ((x) ^ (1LL << (i))) #define ms(d,x) memset(d , x , sizeof(d)) #define exist __exist #define ends __ends #define visit visited #define left __left #define right __right #define prev __prev #define next __next #define sitingfake 1 #define orz 1 //constant const long long mod = 1e9 + 7; const long long linf = 4557430888798830399LL; const long long nlinf = -4485090715960753727LL; const int LOG = 20; const int inf = 1061109567; const int ninf = -1044266559; const int dx[] = {0 , -1 , 0 , 1}; const int dy[] = {-1 , 0 , 1 , 0}; template<typename T> bool maximize(T &a, const T &b) { if(a < b) {a = b; return 1;} return 0; } template<typename T> bool minimize(T &a, const T &b) { if(a > b) {a = b; return 1;} return 0; } void Plus(ll & a ,ll b) { b %= mod; a += b; if(a < 0) a += mod; a %= mod; return; } void Mul(ll & a, ll b) { (a *= (b % mod)) %= mod; return; } //code const int maxn = 1e6 + 7; string s; int n , k; int a[maxn] , b[maxn] , pref[maxn] , timerA , timerB; namespace sub3 { int dp[2][5005]; int cost[5005][5005]; void compute() { for(int l = 1; l <= n; l++) { for(int r = l; r <= n; r++) { if(a[r] > b[l]) { cost[l][r] = cost[l][r - 1] + pref[a[r]] - pref[b[l] - 1]; } else cost[l][r] = cost[l][r - 1]; } } } void DnC(int l , int r, int optl , int optr , int cur) { if(l > r) return; int mid = (r + l) >> 1; int optk; dp[cur][mid] = inf; for(int i = optl; i <= min(mid , optr); i++) { if(minimize(dp[cur][mid] , dp[!cur][i - 1] + cost[i][mid])) { optk = i; } } DnC(l , mid - 1 , optl , optk , cur); DnC(mid + 1 , r , optk , optr , cur); } void solve() { ms(dp , 0x3f); dp[0][0] = 0; compute(); for(int i = 1; i <= n; i++) { dp[1][i] = cost[1][i]; } for(int i = 2; i <= k; i++) { DnC(i , n , 1 , n , i & 1); } cout << dp[k & 1][n]; } } namespace sub5 { ll cnt[2 * maxn]; ll sumpref[2 * maxn]; int pos[maxn]; pair <ll , int> dp[maxn]; int opt[maxn]; ll cost(int l , int r) { if(a[r] < b[l]) return 0; return -pref[b[l] - 1] * (cnt[a[r]] - cnt[pos[l] - 1]) + sumpref[a[r]] - sumpref[pos[l] - 1]; } pair <ll , int> compute(ll lambda) { dp[0] = {0 , 0}; opt[0] = 1; for(int i = 1; i <= n; i++) { dp[i] = {linf , inf}; for(int j = i; j >= 1; j--) { minimize(dp[i] , {dp[j - 1].fi + cost(j , i) + lambda , dp[j - 1].se + 1}); } } return dp[n]; } void solve() { for(int i = 1; i <= 2 * n; i++) { if(s[i - 1] == 'A') { sumpref[i] = pref[i]; cnt[i] = 1; } sumpref[i] += sumpref[i - 1]; cnt[i] += cnt[i - 1]; } for(int i = 1; i <= n; i++) { pos[i] = max(a[i] , b[i]); } ll left = 0 , right = 1e12 , ans = 0; while(left <= right) { ll mid = (left + right) >> 1; if(compute(mid).se <= k) { ans = mid; right = mid - 1; } else left = mid + 1; } pair <ll , int> tmp = compute(ans); cout << tmp.fi - 1ll * ans * tmp.se; } } void solve(void) { cin >> n >> k; cin >> s; for(int i = 1; i <= 2 * n; i++) { pref[i] = pref[i - 1]; if(s[i - 1] == 'A') { a[i] = 0; a[++timerA] = i; } else { a[i] = 1; pref[i] += 1; b[++timerB] = i; } } sub5 :: solve(); } /** 5 3 AABABABBAB **/ signed main() { ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0); #define task "" if(fopen(task".inp","r")) { freopen(task".inp","r",stdin); freopen(task".out","w",stdout); } int tc = 1; // cin >> tc; while(tc--) solve(); // execute; }

chorus.cpp: In function 'int main()':
chorus.cpp:222:15: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  222 |        freopen(task".inp","r",stdin);
      |        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
chorus.cpp:223:15: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  223 |        freopen(task".out","w",stdout);
      |        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~