Submission #147028

#	Time	Username	Problem	Language	Result	Execution time	Memory
147028		ijk1111	Watching (JOI13_watching)	C++14	50 / 100	178 ms	3748 KiB

watching

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

#define N 2001
int n, p, q, a[N], dp[N][N];

int binsearch(int l, int r, int x) {
        int i = (l+r)/2;

        while (l != i && i != r) {
                if (a[i] <= x)
                        l = i;
                else
                        r = i;

                i = (l+r)/2;
        }

        for (int i = l; i <= r; i++)
                if (a[i] > x)
                        return i;
        return n+1;
}

bool check(int w) {
        for (int i = 0; i <= p; i++)
                for (int j = 0; j <= q; j++)
                        dp[i][j] = 0;

        dp[0][1] = binsearch(1, n, a[1]+2*w-1)-1;
        dp[1][0] = binsearch(1, n, a[1]+w-1)-1;
        for (int i = 1; i <= p; i++)
                for (int j = 1; j <= q; j++) {
                        int tmp1 = binsearch(1, n, a[dp[i-1][j]+1]+w-1) - 1;
                        int tmp2 = binsearch(1, n, a[dp[i][j-1]+1]+2*w-1) - 1;

                        dp[i][j] = max(dp[i-1][j], max(dp[i][j-1], max(tmp1, tmp2)));

                        if (dp[i][j] == n)
                                return true;
                }

        return false;
}

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

        if (p+q >= n) {
                printf("%d \n", 1);

                return 0;
        }

        sort(a+1, a+1+n);

        int l = 1, r = 1000000000, ans = 0;

        while (l <= r) {
                int mid = (l+r)/2;

                if (check(mid)) {
                        ans = mid;
                        r = mid-1;
                }
                else l = mid+1;
        }

        printf("%d \n", ans);

        return 0;
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:47:14: 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:49:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
                 scanf("%d", &a[i]);
                 ~~~~~^~~~~~~~~~~~~

• Subtask 1: 50 / 50
• Subtask 2: 0 / 50