Submission #968066

#	Time	Username	Problem	Language	Result	Execution time	Memory
968066		weakweakweak	Line Town (CCO23_day1problem3)	C++17	0 / 25	1 ms	4444 KiB

Main

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

int n, a[500010], pre[500100], suf[500100];

int main () {
    ios_base::sync_with_stdio(false); cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i];
    for (int i = 0; i <= n; i++) pre[i] = suf[i] = INT_MAX / 3;
    pre[0] = 0;
    for (int i = 1; i <= n; i++) {
        if (a[i] == -1) pre[i] = pre[i - 1];
        if (i > 1 and a[i] == 1 and a[i - 1] == 1) pre[i] = min(pre[i], pre[i - 2] + 1);
    }
    suf[0] = 0;
    for (int i = 1; i <= n; i++) {
        int j = n + 1 - i;
        if (a[j] == 1) suf[i] = suf[i - 1];
        if (i > 1 and a[j] == -1 and a[j + 1] == -1) suf[i] = min(suf[i], suf[i - 2] + 1); 
    }

    int ans = suf[0] + pre[n];
    for (int i = 1; i <= n; i++) ans = min(ans, suf[i - 1] + pre[n - i]);

    if (ans > n / 2) ans = -1;
    cout << ans << '\n';
return 0;}

• Subtask 1: 0 / 3
• Subtask 2: 0 / 3
• Subtask 3: 0 / 3
• Subtask 4: 0 / 4
• Subtask 5: 0 / 4
• Subtask 6: 0 / 3
• Subtask 7: 0 / 2
• Subtask 8: 0 / 3