萌新求调简单dp
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萌新求调简单dp
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ttq012楼主2025/6/19 16:38

wa 38 39 40 这三个答案为 No 的点

#pragma GCC optimize(3, "Ofast", "inline", "unroll-loops")
#include <bits/stdc++.h>
#define int long long
using namespace std;

const int N = 1000010;
const int inf = 1e18;

int l[N], r[N], f[N], vis[N], vis2[N];
int to_l[N], to_r[N];

inline int calc(int l, int r)
{
    if ((r - l + 1) & 1)
        return 0;
    int len = r - l + 1, ll = l;
    int mid = l + len / 2;
    while (mid <= r)
    {
        if (to_r[l] && to_r[l] != mid)
            return 0;
        if (to_l[mid] && to_l[mid] != l)
            return 0;
        if (to_l[mid] && to_r[l] && vis[l] != -vis[mid])
            return 0;
        if (vis[l] < 0 || vis[mid] > 0)
            return 0;
        ++l, ++mid;
    }
    for (int i = ll; i <= r; ++i)
        if ((to_l[i] && to_l[i] < ll) || to_r[i] > r)
            return 0;
    return 1;
}

signed main()
{
    cin.tie(0)->sync_with_stdio(false);
    int n;
    cin >> n;
    for (int i = 1; i <= n; ++i)
    {
        cin >> l[i] >> r[i];
        if (~l[i])
        {
            if (vis[l[i]])
            {
                cout << "No\n";
                return 0;
            }
            vis[l[i]] = i;
        }
        if (~r[i])
        {
            if (vis[r[i]])
            {
                cout << "No\n";
                return 0;
            }
            vis[r[i]] = -i;
        }
        if (~l[i] && ~r[i])
        {
            if (l[i] >= r[i])
            {
                cout << "No\n";
                return 0;
            }
            if (!to_l[r[i]])
                to_l[r[i]] = l[i];
            else
                to_l[r[i]] = min(to_l[r[i]], l[i]);
            if (!to_r[l[i]])
                to_r[l[i]] = r[i];
            else
                to_r[l[i]] = max(to_r[l[i]], r[i]);
        }
    }
    f[0] = 1;
    for (int i = 1; i <= n * 2; ++i)
        for (int j = 1; j <= i; ++j)
            if (f[j - 1] && calc(j, i))
            {
                f[i] = 1;
                break;
            }
    // cerr << "f: ";
    // for (int i = 1; i <= n * 2; ++i)
    //     cerr << f[i] << ' ';
    // cerr << '\n';
    cout << (f[n * 2] ? "Yes" : "No") << '\n';
    return 0;
}
2025/6/19 16:38
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