Submission #863942

#	Time	Username	Problem	Language	Result	Execution time	Memory
863942		prohacker	Watching (JOI13_watching)	C++14	100 / 100	204 ms	16216 KiB

watching

#include <bits/stdc++.h>
#define ll long long
#define ld long double

using namespace std;

const int N = 2010;
const int INF = INT_MAX;
const int mod = 1e9+7;

int n,p,q,a[N];
int dp[N][N];

bool check(int mid) {
    for(int i = 1 ; i <= n ; i++) {
        for(int j = 0 ; j <= q ; j++) {
            dp[i][j] = mod;
        }
    }
    for(int i = 1, j = 1, k = 1 ; i <= n ; i++) {
        while(j < i && a[i]-a[j] >= mid) {
            j++;
        }
        while(k < i && a[i]-a[k] >= mid*2) {
            k++;
        }
        for(int l = 0 ; l <= q ; l++) {
            dp[i][l] = dp[j-1][l]+1;
        }
        for(int l = 0 ; l <= q ; l++) {
            dp[i][l+1] = min(dp[i][l+1],dp[k-1][l]);
        }
    }
    for(int i = 0 ; i <= q  ; i++) {
        if(dp[n][i] <= p) {
            return true;
        }
    }
    return false;
}

signed main()
{
    if (fopen("WATCHING.inp", "r")) {
        freopen("WATCHING.inp", "r", stdin);
        freopen("WATCHING.out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> p >> q;
    if(n <= p+q) {
        cout << 1;
        return 0;
    }
    for(int i = 1 ; i <= n ; i++) {
        cin >> a[i];
    }
    sort(a+1,a+n+1);
    int l = 1;
    int r = 1e9;
    int ans;
    while(l <= r) {
        int mid = l + r >> 1;
        if(check(mid)) {
            ans = mid;
            r = mid-1;
        }
        else {
            l = mid+1;
        }
    }
    cout << ans;
    return 0;
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:64:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   64 |         int mid = l + r >> 1;
      |                   ~~^~~
watching.cpp:45:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   45 |         freopen("WATCHING.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
watching.cpp:46:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   46 |         freopen("WATCHING.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
watching.cpp:73:13: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   73 |     cout << ans;
      |             ^~~

• Subtask 1: 50 / 50
• Subtask 2: 50 / 50