oj.uz

Submission #43790

# Submission time Handle Problem Language Result Execution time Memory
43790 2018-03-23T19:02:22 Z evpipis Watching (JOI13_watching) C++11
50 / 100
 1000 ms 32372 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;
}

void read(int &res){
    char c;
    while (c = getchar(), c < '0' || c > '9'){}
    res = c-'0';
    while (c = getchar(), c >= '0' && c <= '9')
        res = 10*res+c-'0';
}

int main(){
    read(n), read(p), read(q);
    for (int i = 1; i <= n; i++)
        read(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 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 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 1 ms 1144 KB Output is correct
7 Correct 2 ms 1316 KB Output is correct
8 Correct 2 ms 1316 KB Output is correct
9 Correct 3 ms 1444 KB Output is correct
10 Correct 3 ms 1444 KB Output is correct
11 Correct 3 ms 1456 KB Output is correct
12 Correct 4 ms 1456 KB Output is correct
13 Correct 2 ms 1456 KB Output is correct
14 Correct 2 ms 1456 KB Output is correct
15 Correct 2 ms 1460 KB Output is correct

Subtask #2
0 / 50.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 16620 KB Output is correct
2 Correct 2 ms 16620 KB Output is correct
3 Correct 2 ms 16620 KB Output is correct
4 Correct 2 ms 16620 KB Output is correct
5 Correct 2 ms 16620 KB Output is correct
6 Correct 2 ms 16620 KB Output is correct
7 Correct 19 ms 17004 KB Output is correct
8 Correct 126 ms 18796 KB Output is correct
9 Correct 115 ms 18796 KB Output is correct
10 Correct 146 ms 18796 KB Output is correct
11 Correct 152 ms 18796 KB Output is correct
12 Execution timed out 1045 ms 32372 KB Time limit exceeded
13 Halted 0 ms 0 KB -