oj.uz

Submission #43789

# Submission time Handle Problem Language Result Execution time Memory
43789 2018-03-23T18:57:59 Z evpipis Watching (JOI13_watching) C++11
50 / 100
 1000 ms 32400 KB 
#include <bits/stdc++.h>
using namespace std;

const int len = 2e3+5, inf = 1e9;
int n, p, q, pp, qq, a[len];
int nex[2][len], pre[2][len], dp[len][len], best[len][len];

int finduse(int pos, int use1){
    if (pos == 0 && use1 == 0) return 0;
    if (pos == 0 && use1 != 0) return inf;
    if (best[pos][use1] != -1) return best[pos][use1];

    int ans = inf;
    if (use1 > 0)
        ans = min(ans, finduse(pre[0][pos], use1-1));
    ans = min(ans, finduse(pre[1][pos], use1)+1);

    return best[pos][use1] = ans;
}

int solve(int pos, int use1){
    if (pos == n+1) return 1;
    if (dp[pos][use1] != -1) return dp[pos][use1];

    int use2 = finduse(pos-1, use1), ans = 0;
    if (use1 < pp)
        ans = max(ans, solve(nex[0][pos], use1+1));
    if (use2 < qq)
        ans = max(ans, solve(nex[1][pos], use1));

    //if (hey) printf("pos = %d, use1 = %d, use2 = %d, ans = %d\n", pos, use1, use2, ans);
    return dp[pos][use1] = ans;
}

bool check(int w){
    for (int i = 1, j1 = 1, j2 = 1; i <= n; i++){
        while (j1 <= n && a[j1]-a[i]+1 <= w) j1++;
        while (j2 <= n && a[j2]-a[i]+1 <= 2*w) j2++;

        nex[0][i] = j1;
        nex[1][i] = j2;
    }

    for (int i = n, j1 = n, j2 = n; i >= 1; i--){
        while (j1 >= 1 && a[i]-a[j1]+1 <= w) j1--;
        while (j2 >= 1 && a[i]-a[j2]+1 <= 2*w) j2--;

        pre[0][i] = j1;
        pre[1][i] = j2;
    }

    qq = q, pp = p;
    if (q < p){
        swap(pp, qq);
        for (int i = 1; i <= n; i++){
            swap(nex[0][i], nex[1][i]);
            swap(pre[0][i], pre[1][i]);
        }
    }

    for (int i = 0; i <= n; i++)
        for (int j = 0; j <= pp; j++)
            dp[i][j] = best[i][j] = -1;

    return solve(1, 0);
}

int bs(){
    int l = 1, r = (inf+p+q)/(p+q), ans;
    while (l <= r){
        int mid = (l+r)/2;
        if (check(mid)){
            ans = mid;
            r = mid-1;
        }
        else
            l = mid+1;
    }

    return ans;
}

int main(){
    scanf("%d %d %d", &n, &p, &q);
    for (int i = 1; i <= n; i++)
        scanf("%d", &a[i]);
    sort(a+1, a+n+1);

    if (p+q >= n) printf("1\n");
    else printf("%d\n", bs());
    return 0;
}

Compilation message

watching.cpp: In function 'int main()':
watching.cpp:84:34: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d %d", &n, &p, &q);
                                  ^
watching.cpp:86:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d", &a[i]);
                           ^
watching.cpp: In function 'int bs()':
watching.cpp:80:12: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
     return ans;
            ^

Subtask #1
50.0 / 50.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 1144 KB Output is correct
2 Correct 2 ms 1144 KB Output is correct
3 Correct 2 ms 1144 KB Output is correct
4 Correct 2 ms 1144 KB Output is correct
5 Correct 2 ms 1144 KB Output is correct
6 Correct 2 ms 1144 KB Output is correct
7 Correct 3 ms 1496 KB Output is correct
8 Correct 3 ms 1496 KB Output is correct
9 Correct 3 ms 1496 KB Output is correct
10 Correct 3 ms 1496 KB Output is correct
11 Correct 3 ms 1496 KB Output is correct
12 Correct 4 ms 1496 KB Output is correct
13 Correct 2 ms 1496 KB Output is correct
14 Correct 2 ms 1496 KB Output is correct
15 Correct 3 ms 1496 KB Output is correct

Subtask #2
0 / 50.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 16624 KB Output is correct
2 Correct 2 ms 16624 KB Output is correct
3 Correct 2 ms 16624 KB Output is correct
4 Correct 2 ms 16624 KB Output is correct
5 Correct 3 ms 16624 KB Output is correct
6 Correct 2 ms 16624 KB Output is correct
7 Correct 19 ms 17000 KB Output is correct
8 Correct 147 ms 18676 KB Output is correct
9 Correct 123 ms 18700 KB Output is correct
10 Correct 147 ms 18700 KB Output is correct
11 Correct 162 ms 18700 KB Output is correct
12 Execution timed out 1069 ms 32400 KB Time limit exceeded
13 Halted 0 ms 0 KB -