#include <bits/stdc++.h> using namespace std; const int N = 500000 + 50; const int INF = 2000000000 + 50; int t[N]; int a[N]; int dp[N]; long long pref[N]; int order[N], pos[N]; int n; bool comp(int x, int y) { return pref[x] < pref[y]; } inline void Update(int pos, int val) { for (int i = pos; i < N; i += i&-i) { t[i] = min(t[i], val); } } inline int PrefMin(int r) { int ans = INF; while(r > 0) { ans = min(ans, t[r]); r -= r&-r; } return ans; } int main() { ios_base::sync_with_stdio(0); cin.tie(0); cin >> n; for (int i = 1; i <= n; i++) { cin >> a[i]; pref[i] = a[i] + pref[i - 1]; order[i] = i; } sort(order, order + n + 1, comp); int prev_pos = 0; for (int i = 0; i <= n; i++) { if (i != 0 && pref[order[i]] == pref[order[i - 1]]) { pos[order[i]] = prev_pos; } else { pos[order[i]] = ++prev_pos; } } fill(t, t + N, INF); Update(pos[0], 0); for (int i = 1; i <= n; i++) { if (a[i] >= 0) { dp[i] = dp[i - 1]; } else { dp[i] = INF; } dp[i] = min(dp[i], i - 1 + PrefMin(pos[i])); Update(pos[i], -i + dp[i]); } if (dp[n] >= INF) { dp[n] = -1; } cout << dp[n]; return 0; }
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 | #include <bits/stdc++.h> using namespace std; const int N = 500000 + 50; const int INF = 2000000000 + 50; int t[N]; int a[N]; int dp[N]; long long pref[N]; int order[N], pos[N]; int n; bool comp(int x, int y) { return pref[x] < pref[y]; } inline void Update(int pos, int val) { for (int i = pos; i < N; i += i&-i) { t[i] = min(t[i], val); } } inline int PrefMin(int r) { int ans = INF; while(r > 0) { ans = min(ans, t[r]); r -= r&-r; } return ans; } int main() { ios_base::sync_with_stdio(0); cin.tie(0); cin >> n; for (int i = 1; i <= n; i++) { cin >> a[i]; pref[i] = a[i] + pref[i - 1]; order[i] = i; } sort(order, order + n + 1, comp); int prev_pos = 0; for (int i = 0; i <= n; i++) { if (i != 0 && pref[order[i]] == pref[order[i - 1]]) { pos[order[i]] = prev_pos; } else { pos[order[i]] = ++prev_pos; } } fill(t, t + N, INF); Update(pos[0], 0); for (int i = 1; i <= n; i++) { if (a[i] >= 0) { dp[i] = dp[i - 1]; } else { dp[i] = INF; } dp[i] = min(dp[i], i - 1 + PrefMin(pos[i])); Update(pos[i], -i + dp[i]); } if (dp[n] >= INF) { dp[n] = -1; } cout << dp[n]; return 0; } |