oj.uz

Submission #43786

# Submission time Handle Problem Language Result Execution time Memory
43786 2018-03-23T18:43:10 Z evpipis Watching (JOI13_watching) C++11
50 / 100
 1000 ms 32720 KB 
#include <bits/stdc++.h>
using namespace std;

const int len = 2e3+5, inf = 1e9;
int n, p, q, 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 < p)
        ans = max(ans, solve(nex[0][pos], use1+1));
    if (use2 < q)
        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){
    //printf("START CHECK: w = %d\n", 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;
    }

    /*if (w == 14){
    for (int i = 1; i <= n; i++)
        printf("i = %d, nex = (%d, %d), pre = (%d, %d)\n", i, nex[0][i], nex[1][i], pre[0][i], pre[1][i]);
    }*/

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

    return solve(1, 0);
}

int bs(){
    int l = 1, r = inf, ans;
    while (l <= r){
        int mid = (l+r)/2;
        //printf("mid = %d\n", mid);
        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:82:34: 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:84:27: 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:78:12: 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 1 ms 1144 KB Output is correct
3 Correct 2 ms 1144 KB Output is correct
4 Correct 1 ms 1144 KB Output is correct
5 Correct 1 ms 1144 KB Output is correct
6 Correct 2 ms 1144 KB Output is correct
7 Correct 2 ms 1532 KB Output is correct
8 Correct 2 ms 1532 KB Output is correct
9 Correct 2 ms 1560 KB Output is correct
10 Correct 3 ms 1560 KB Output is correct
11 Correct 4 ms 1560 KB Output is correct
12 Correct 5 ms 1560 KB Output is correct
13 Correct 2 ms 1560 KB Output is correct
14 Correct 2 ms 1560 KB Output is correct
15 Correct 2 ms 1560 KB Output is correct

Subtask #2
0 / 50.0

# Verdict Execution time Memory Grader output
1 Correct 15 ms 16908 KB Output is correct
2 Correct 1 ms 16908 KB Output is correct
3 Correct 2 ms 16908 KB Output is correct
4 Correct 2 ms 16908 KB Output is correct
5 Correct 2 ms 16908 KB Output is correct
6 Correct 2 ms 16908 KB Output is correct
7 Correct 19 ms 17188 KB Output is correct
8 Correct 138 ms 19016 KB Output is correct
9 Correct 323 ms 29020 KB Output is correct
10 Correct 887 ms 32720 KB Output is correct
11 Correct 172 ms 32720 KB Output is correct
12 Execution timed out 1034 ms 32720 KB Time limit exceeded
13 Halted 0 ms 0 KB -