Submission #30637

#TimeUsernameProblemLanguageResultExecution timeMemory
30637NirjhorSplit the sequence (APIO14_sequence)C++14
0 / 100
0 ms1848 KiB
#include <bits/stdc++.h> using namespace std; typedef long long ll; const int K = 205; const int N = 100005; struct line { int id; ll m, c; }; int n, k, ptr; ll a[N], f[K][N]; int pre[K][N]; vector <line> v[K]; stack <int> opts; // dp(i, k) = dp(j, k - 1) + a[j] * a[i] - a[j]^2 // y = m1x + c1, y = m2x + c2, y = m3x + c3 // x = (c1 - c2)/(m2 - m1) // x = (c1 - c3)/(m3 - m1) // (c1 - c3) * (m2 - m1) < (c1 - c2) * (m3 - m1) bool bad (line i, line j, line k) { return (i.c - k.c) * (j.m - i.m) < (i.c - j.c) * (k.m - i.m); } void add (int at, line l) { v[at].push_back(l); while (v[at].size() >= 3 and bad(v[at][v[at].size() - 3], v[at][v[at].size() - 2], v[at][v[at].size() - 1])) { v[at].erase(v[at].end() - 2); } } line query (int at, ll x) { while (ptr < v[at].size() - 1 and v[at][ptr].m * x + v[at][ptr].c < v[at][ptr + 1].m * x + v[at][ptr + 1].c) { ++ptr; } return v[at][ptr]; } int main() { scanf("%d %d", &n, &k); for (int i = 1; i <= n; ++i) { scanf("%lld", a + i); a[i] += a[i - 1]; } for (int i = 1; i <= n; ++i) { add(0, {i, a[i], -a[i] * a[i]}); } for (int i = 1; i <= k; ++i) { ptr = 0; add(i - 1, {0, 0, 0}); for (int j = 1; j <= n; ++j) { line opt = query(i - 1, a[j]); f[i][j] = opt.m * a[j] + opt.c; pre[i][j] = opt.id; add(i - 1, {j, a[j], f[i - 1][j] - a[j] * a[j]}); } } printf("%lld\n", f[k][n]); for (int i = k, j = n; i; --i) { j = pre[i][j]; opts.push(j); } while (!opts.empty()) { printf("%d ", opts.top()); opts.pop(); } puts(""); return 0; }

Compilation message (stderr)

sequence.cpp: In function 'line query(int, ll)':
sequence.cpp:40:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while (ptr < v[at].size() - 1 and v[at][ptr].m * x + v[at][ptr].c < v[at][ptr + 1].m * x + v[at][ptr + 1].c) {
              ^
sequence.cpp: In function 'int main()':
sequence.cpp:47:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &n, &k);
                         ^
sequence.cpp:49:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld", a + i);
                         ^
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