Submission #353336

#	Time	Username	Problem	Language	Result	Execution time	Memory
353336		dolphingarlic	Ancient Books (IOI17_books)	C++14	100 / 100	445 ms	137708 KiB

books

#include "books.h"

#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

int crit_l, crit_r;
int cmp[1000000], cmp_l[1000000], cmp_r[1000000];
map<pair<int, int>, ll> dp;

void extend(int &l, int &r) {
    int ext_l = min(cmp_l[cmp[l]], cmp_l[cmp[r]]);
    int ext_r = max(cmp_r[cmp[l]], cmp_r[cmp[r]]);
    while (l != ext_l || r != ext_r) {
        if (l != ext_l) {
            l--;
            ext_l = min(ext_l, cmp_l[cmp[l]]);
            ext_r = max(ext_r, cmp_r[cmp[l]]);
        } else {
            r++;
            ext_l = min(ext_l, cmp_l[cmp[r]]);
            ext_r = max(ext_r, cmp_r[cmp[r]]);
        }
    }
}

ll compute(int l, int r) {
    extend(l, r);
    if (dp.count({l, r})) return dp[{l, r}];
    if (l == crit_l) return dp[{l, r}] = compute(l, r + 1) + 2;
    if (r == crit_r) return dp[{l, r}] = compute(l - 1, r) + 2;
    ll to_l = 2, to_r = 2;
    int nl, nr, tl, tr;
    nl = l - 1, nr = r, tl = l, tr = r + 1;
    extend(nl, nr), extend(tl, tr);
    while (nl != crit_l && nr < tr) {
        to_l += 2;
        nl--;
        extend(nl, nr);
    }
    if (nr < tr) return dp[{l, r}] = to_l + compute(nl, nr);
    nl = l, nr = r + 1, tl = l - 1, tr = r;
    extend(nl, nr), extend(tl, tr);
    while (nr != crit_r && nl > tl) {
        to_r += 2;
        nr++;
        extend(nl, nr);
    }
    return dp[{l, r}] = min(to_l, to_r) + compute(nl, nr);
}

ll minimum_walk(vector<int> p, int s) {
    int n = p.size(), cmp_cnt = 0;
    fill(cmp, cmp + n, -1);
    crit_l = s, crit_r = s;
    ll intra = 0;
    for (int i = 0; i < n; i++) {
        intra += abs(p[i] - i);
        if (cmp[i] == -1) {
            int curr = i;
            cmp_l[cmp_cnt] = cmp_r[cmp_cnt] = i;
            do {
                cmp[curr] = cmp_cnt;
                cmp_r[cmp_cnt] = max(cmp_r[cmp_cnt], curr);
                curr = p[curr];
            } while (curr != i);
            if (i != p[i]) {
                crit_l = min(crit_l, cmp_l[cmp_cnt]);
                crit_r = max(crit_r, cmp_r[cmp_cnt]);
            }
            cmp_cnt++;
        }
    }
    dp[{crit_l, crit_r}] = 0;
    return intra + compute(s, s);
}

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 28 / 28
• Subtask 4: 20 / 20
• Subtask 5: 30 / 30