Submission #118575

#	Time	Username	Problem	Language	Result	Execution time	Memory
118575		IOrtroiii	Skyscraper (JOI16_skyscraper)	C++14	100 / 100	144 ms	19468 KiB

skyscraper

#include <bits/stdc++.h>

using namespace std;

const int N = 105;
const int M = 1005;
const int mod = 1e9 + 7;

void add(int &x, int y) {
   x += y; if (x >= mod) x -= mod;
}

int mul(int x, int y) {
   return (long long) x * y % mod;
}

int a[N];
int f[N][N][M][2][2];

int main() {
   int n, m;
   scanf("%d %d", &n, &m);
   if (n == 1) {
      puts("1");
      return 0;
   }
   for (int i = 1; i <= n; ++i) {
      scanf("%d", a + i);
   }
   sort(a + 1, a + 1 + n);
   for (int i = n; i > 1; --i) {
      a[i] -= a[i - 1];
   }
   a[1] = 0;
   f[0][0][0][0][0] = 1;
   for (int i = 0; i < n; ++i) {
      for (int j = 0; j <= i; ++j) {
         for (int k = 0; k <= m; ++k) {
            for (int l = 0; l < 2; ++l) {
               for (int r = 0; r < 2; ++r) {
                  int ways = f[i][j][k][l][r];
                  if (!ways) continue;
                  int nk = k + a[i + 1] * (2 * j - l - r);
                  if (nk > m) continue;
                  // fix left
                  if (!l) {
                     int coef = j - r;
                     if (i == n - 1) coef += r;
                     add(f[i + 1][j][nk][1][r], mul(coef, ways));
                     add(f[i + 1][j + 1][nk][1][r], ways);
                  }
                  // fix right
                  if (!r) {
                     int coef = j - l;
                     if (i == n - 1) coef += l;
                     add(f[i + 1][j][nk][l][1], mul(coef, ways));
                     add(f[i + 1][j + 1][nk][l][1], ways);
                  }
                  // merge one (not fix)
                  add(f[i + 1][j][nk][l][r], mul(2 * j - l - r, ways));
                  // make new (now fix)
                  add(f[i + 1][j + 1][nk][l][r], ways);
                  // merge two
                  if (j > 1) {
                     int coef = (j - l - r) * (j - 1);
                     // left
                     if (i == n - 1) {
                        coef += (l && r);
                     }
                     add(f[i + 1][j - 1][nk][l][r], mul(coef, ways));
                  }
               }
            }
         }
      }
   }
   int ans = 0;
   for (int i = 0; i <= m; ++i) {
      add(ans, f[n][1][i][1][1]);
   }
   printf("%d\n", ans);
}

Compilation message (stderr)

skyscraper.cpp: In function 'int main()':
skyscraper.cpp:22:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d %d", &n, &m);
    ~~~~~^~~~~~~~~~~~~~~~~
skyscraper.cpp:28:12: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
       scanf("%d", a + i);
       ~~~~~^~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 80 / 80