68 lines
1.3 KiB
C++
68 lines
1.3 KiB
C++
#include <bits/stdc++.h> // {{{
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// https://codeforces.com/blog/entry/96344
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#pragma GCC optimize("O2,unroll-loops")
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#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
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using namespace std;
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using i32 = int32_t;
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using u32 = uint32_t;
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using i64 = int64_t;
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using u64 = uint64_t;
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using f64 = double;
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using f128 = long double;
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// }}}
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void solve() {
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u32 n;
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cin >> n;
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vector<u32> a(n);
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for (u32 i = 0; i < n; ++i) {
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cin >> a[i];
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}
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vector<i64> prefix_one(n + 1, 0), postfix_zero(n + 2, 0);
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for (u32 i = 0; i < n; ++i) {
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prefix_one[i + 1] = (a[i] == 1) + prefix_one[i];
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}
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for (i32 i = n - 1; i >= 0; --i) {
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postfix_zero[i + 1] = postfix_zero[i + 2] + (a[i] == 0);
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}
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postfix_zero[0] = postfix_zero[1];
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i64 ans = 0;
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for (u32 i = 0; i < n; ++i) {
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if (a[i] == 1)
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ans += postfix_zero[i + 2];
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}
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i64 init = ans;
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for (u32 i = 0; i < n; ++i) {
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if (a[i] == 0)
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ans = max(ans, init + postfix_zero[i + 2] - prefix_one[i]);
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else if (a[i] == 1)
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ans = max(ans, init + prefix_one[i] - postfix_zero[i + 2]);
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// } else { // NOTE: forgot 0->1 is possible
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// }
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}
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cout << ans << '\n';
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}
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int main() { // {{{
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cin.tie(nullptr)->sync_with_stdio(false);
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cin.exceptions(cin.failbit);
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int tc = 1;
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cin >> tc;
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for (int t = 0; t < tc; ++t) {
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solve();
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}
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return 0;
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}
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// }}}
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