#include <bits/stdc++.h> using namespace std; typedef long long int LL; const int N = 5e5 + 7; const int T = 1 << 19; const int INF = 1e9 + 7; int n; int order[N]; int input[N]; int dp[N]; int tree[T + T]; void get_order() { LL sum = 0; map <LL, int> M; vector <LL> pref = {0}; for (int i = 1; i <= n; ++i) { sum += input[i]; pref.push_back(sum); } sort(pref.begin(), pref.end()); pref.erase(unique(pref.begin(), pref.end()), pref.end()); for (int i = 0; i < (int)pref.size(); ++i) M[pref[i]] = i; sum = 0; order[0] = M[sum]; for (int i = 1; i <= n; ++i) { sum += input[i]; order[i] = M[sum]; } } void read() { scanf("%d", &n); for(int i = 1; i <= n; ++i) scanf("%d", &input[i]); get_order(); } void update(int p, int v) { p += T; while(p) { tree[p] = min(tree[p], v); p >>= 1; } } int ask(int from, int to) { int ret = INF; from += T, to += T; while(from <= to) { if(from & 1) ret = min(ret, tree[from]); if(!(to & 1)) ret = min(ret, tree[to]); from = (from + 1) >> 1; to = (to - 1) >> 1; } return ret; } void solve() { for(int i = 1; i < T + T; ++i) tree[i] = INF; dp[0] = 0; update(order[0], dp[0]); for(int i = 1; i <= n; ++i) { dp[i] = i + ask(0, order[i]) - 1; update(order[i], dp[i] - i); } } int main() { read(); solve(); printf("%d\n", dp[n] > n ? -1 : 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 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 | #include <bits/stdc++.h> using namespace std; typedef long long int LL; const int N = 5e5 + 7; const int T = 1 << 19; const int INF = 1e9 + 7; int n; int order[N]; int input[N]; int dp[N]; int tree[T + T]; void get_order() { LL sum = 0; map <LL, int> M; vector <LL> pref = {0}; for (int i = 1; i <= n; ++i) { sum += input[i]; pref.push_back(sum); } sort(pref.begin(), pref.end()); pref.erase(unique(pref.begin(), pref.end()), pref.end()); for (int i = 0; i < (int)pref.size(); ++i) M[pref[i]] = i; sum = 0; order[0] = M[sum]; for (int i = 1; i <= n; ++i) { sum += input[i]; order[i] = M[sum]; } } void read() { scanf("%d", &n); for(int i = 1; i <= n; ++i) scanf("%d", &input[i]); get_order(); } void update(int p, int v) { p += T; while(p) { tree[p] = min(tree[p], v); p >>= 1; } } int ask(int from, int to) { int ret = INF; from += T, to += T; while(from <= to) { if(from & 1) ret = min(ret, tree[from]); if(!(to & 1)) ret = min(ret, tree[to]); from = (from + 1) >> 1; to = (to - 1) >> 1; } return ret; } void solve() { for(int i = 1; i < T + T; ++i) tree[i] = INF; dp[0] = 0; update(order[0], dp[0]); for(int i = 1; i <= n; ++i) { dp[i] = i + ask(0, order[i]) - 1; update(order[i], dp[i] - i); } } int main() { read(); solve(); printf("%d\n", dp[n] > n ? -1 : dp[n]); return 0; } |