Submission #1053172

#	Time	Username	Problem	Language	Result	Execution time	Memory
1053172		elazarkoren	Sprinklers (CEOI24_sprinklers)	C++17	100 / 100	42 ms	5180 KiB

Main

#include <bits/stdc++.h>
#define x first
#define y second
#define all(v) v.begin(), v.end()
#define chkmin(a, b) a = min(a, b)
#define chkmax(a, b) a = max(a, b)
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pii;
typedef vector<pii> vii;

const int MAX_N = 1e5 + 5;

ll s[MAX_N], f[MAX_N];
int ri[MAX_N], flip[MAX_N];
int n, m;

bool Solve(int k) {
    int i = 0, j = 0;
    vi leftest(n);
    while (i < n && j < m) {
        flip[i] = 0;
        if (f[j] >= s[i]) {
            leftest[i] = -1;
            while (j < m && f[j] - s[i] <= k) j++;
            ri[i] = 1;
            i++;
            continue;
        }
        if (s[i] - f[j] > k) return 0;
        ri[i] = 0;
        leftest[i] = j;
        if (i && leftest[i - 1] != -1 && s[i] - f[leftest[i - 1]] <= k) {
            flip[i] = 1;
            while (j < m && f[j] - s[i - 1] <= k) j++;
            ri[i - 1] = 1;
        }
        while (j < m && f[j] <= s[i] && s[i] - f[j] <= k) j++;
        i++;
    }
    if (j != m) return 0;
    for (i = n - 1; i >= 0; i--) {
        if (flip[i]) {
            for (j = i; flip[j - 1]; j--);
            j--;
            for (int a = i, b = 0; a >= j; a--, b ^= 1) ri[a] = b;
            i = j + 1;
        }
    }
    return 1;
}

int Solve2(int k) {
    for (int i = 0; i < (1 << n); i++) {
        vii ranges;
        for (int j = 0; j < n; j++) {
            if ((i >> j) & 1) ranges.push_back({s[j], s[j] + k});
            else ranges.push_back({s[j] - k, s[j]});
        }
        sort(all(ranges));
        int a = 0, b = 0;
        while (a < n && b < m) {
            if (ranges[a].x <= f[b] && f[b] <= ranges[a].y) b++;
            else a++;
        }
        if (b == m) {
            return i + 1;
        }
    }
    return 0;
}

int Ans() {
    int begin = 0, end = 1e9 + 1;
    while (begin < end) {
        int mid = (begin + end) >> 1;
//        bool b1 = Solve(mid), b2 = Solve2(mid);
//        if (b1 != b2) {
//            cout << "BAD\n";
//            cout << n << ' ' << m << '\n';
//            for (int i = 0; i < n; i++) cout << s[i] << ' ';
//            cout << '\n';
//            for (int i = 0; i < m; i++) cout << f[i] << ' ';
//            exit(0);
//        }
        if (Solve(mid)) end = mid;
        else begin = mid + 1;
    }
    return end;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
//    while (true) {
//        for (int i = 0; i < n; i++) {
//            s[i] = rand();
//        }
//        for (int i = 0; i < m; i++) {
//            f[i] = rand();
//        }
//        sort(s, s + n);
//        sort(f, f + m);
//        Ans();
//    }
    for (int i = 0; i < n; i++) cin >> s[i];
    for (int i = 0; i < m; i++) cin >> f[i];

    int end = Ans();
//    for (end = 0; end <= 8; end++) {
//        if (Solve(end)) break;
//    }
    int x = Solve(end);
    if (!x) {
        cout << -1 << '\n';
        return 0;
    }
//    x--;
//    for (int i = 0; i < n; i++) {
//        cout << ((x >> i) & 1 ? 'R' : 'L');
//    }
    cout << end << '\n';
    for (int i = 0; i < n; i++) {
        cout << (ri[i] ? 'R' : 'L');
    }
}
/*
3 5
6 14 25
0 13 19 21 28
 */

• Subtask 0: 0 / 0
• Subtask 1: 3 / 3
• Subtask 2: 6 / 6
• Subtask 3: 17 / 17
• Subtask 4: 27 / 27
• Subtask 5: 47 / 47