Submission #50548453

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Source Code Expand

#include <bits/stdc++.h>
#include <atcoder/modint>

namespace {
    using ModInt [[maybe_unused]] = atcoder::modint998244353;
    using Num [[maybe_unused]] = long long int;
    using Vec [[maybe_unused]] = std::vector<Num>;
    using Set [[maybe_unused]] = std::set<Num>;
    using Mset [[maybe_unused]] = std::multiset<Num>;
    using Edges [[maybe_unused]] = std::vector<std::vector<Num>>;

    template<typename T>
    using Q [[maybe_unused]] = std::queue<T>;

    template<typename T>
    using PQ [[maybe_unused]] = std::priority_queue<T, std::vector<T>, std::greater<T>>;
}

Num n {0};
Vec ns;

void solve(std::istream& is, std::ostream& os) {
    is >> n;
    ns.resize(n);

    for(auto&& a : ns) {
        is >> a;
    }

    if (ns.at(0) != 0) {
        os << "No\n";
        return;
    }

    Num n_ones {0};
    Num index {0};
    for(; index<n; ++index) {
        if (ns.at(index) != (index & 1)) {
            break;
        }
        ++n_ones;
    }

    if (index == n) {
        os << "Yes\n";
        return;
    }

    Num prev = 1 - ns.at(index);
    for(; index<n; ++index) {
        Num current = ns.at(index);
        n_ones -= (prev != current);
        prev = current;
    }

    if (ns.back() == 0) {
        ++n_ones;
    }

    if (n_ones >= 0) {
        os << "Yes\n";
    } else {
        os << "No\n";
    }
}

int main(void) {
    solve(std::cin, std::cout);
    return 0;
}

Submission Info

Judge Result