oj.uz

Submission #110841

# Submission time Handle Problem Language Result Execution time Memory
110841 2019-05-12T12:41:37 Z Nicholas_Patrick Kangaroo (CEOI16_kangaroo) C++17
100 / 100
 98 ms 21240 KB 
#include <cstdio>
#include <vector>
#define llc (long long)
#define pm %1000000007
using namespace std;

int memo[2001][1001][3];
int n, s, e;
bool valid(int i, int j, int k){
	if(i<0||i>n)return false;
	if(j<0||j>((n+1)>>1))return false;
	if(k<0||k>2)return false;
	if(j>i)return false;
	// if(i!=n&&k>j)return false;
	// if(k>i&&n!=1)return false;// won't happen
	return true;
}
int main(){
	//obvious goal: find # of perm [0, n) such that tracing 0-1-2 -> zig zag, arr[s]=0, arr[e]=n-1
	//inverted goal: find # of perm [0, n) such that value goes up and down, arr[0]=s, arr[n-1]=e
	//in inverted goal, k can only increase when value to add is s or e, rest: stick to slide
	//honestly, I don't fully understand why the algorithm described in the slide works more practice needed


	scanf("%d%d%d", &n, &s, &e);s--;e--;
	//pertama kalinya aku pakai %d tanpa spasi
	//kelihatannya lebih aman, jadi akan selamanya
	//aku pakai ini kecuali ternyata aku salah
	memo[0][0][0]=1;
	for(int i = 0;i < n;i ++){
		for(int j = 0;j <= (n+1)>>1 && j <= i;j ++){
			for(int k = 0;k <= 2 && k <= j;k ++){
				if(i!=s&&i!=e){//k may not increase
					if(valid(i+1, j+1, k)){//new cc
						memo[i+1][j+1][k]=(memo[i+1][j+1][k]+llc memo[i][j][k]*(j+1-k)) pm;
					}
					//apparently, this step is not needed, it just works on paper :P
					// if(valid(i+1, j, k)){//stick to cc
					// 	memo[i+1][j][k]=(memo[i+1][j][k]+llc memo[i][j][k]*((j<<1)-k)) pm;
					// }
					if(valid(i+1, j-1, k)){//merge cc
						memo[i+1][j-1][k]=(memo[i+1][j-1][k]+llc memo[i][j][k]*(j-1)) pm;
					}
				}else{//k may increase
					if(valid(i+1, j, k+1)){
						memo[i+1][j][k+1]=(memo[i+1][j][k+1]+memo[i][j][k]) pm;
					}
					if(valid(i+1, j+1, k+1)){
						memo[i+1][j+1][k+1]=(memo[i+1][j+1][k+1]+memo[i][j][k]) pm;
					}
				}
			}
		}
	}
	// for(int i = 0;i <= n;i ++){
	// 	for(int j = 0;j <= (n+1)>>1;j ++){
	// 		for(int k = 0;k <= 2;k ++){
	// 			printf("%d ", memo[i][j][k]);
	// 		}
	// 		printf("\n");
	// 	}
	// 	printf("\n");
	// }
	printf("%d\n", memo[n][1][2]);
}

Compilation message

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:25:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d", &n, &s, &e);s--;e--;
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 256 KB Output is correct
2 Correct 2 ms 384 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 256 KB Output is correct
2 Correct 2 ms 384 KB Output is correct
3 Correct 2 ms 384 KB Output is correct
4 Correct 2 ms 512 KB Output is correct
5 Correct 3 ms 512 KB Output is correct
6 Correct 2 ms 512 KB Output is correct
7 Correct 2 ms 512 KB Output is correct
8 Correct 2 ms 512 KB Output is correct
9 Correct 2 ms 512 KB Output is correct
10 Correct 4 ms 512 KB Output is correct
11 Correct 2 ms 512 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 256 KB Output is correct
2 Correct 2 ms 384 KB Output is correct
3 Correct 2 ms 384 KB Output is correct
4 Correct 2 ms 512 KB Output is correct
5 Correct 3 ms 512 KB Output is correct
6 Correct 2 ms 512 KB Output is correct
7 Correct 2 ms 512 KB Output is correct
8 Correct 2 ms 512 KB Output is correct
9 Correct 2 ms 512 KB Output is correct
10 Correct 4 ms 512 KB Output is correct
11 Correct 2 ms 512 KB Output is correct
12 Correct 4 ms 1280 KB Output is correct
13 Correct 4 ms 1152 KB Output is correct
14 Correct 7 ms 1280 KB Output is correct
15 Correct 5 ms 1280 KB Output is correct
16 Correct 5 ms 1280 KB Output is correct
17 Correct 4 ms 1324 KB Output is correct
18 Correct 3 ms 1152 KB Output is correct
19 Correct 3 ms 1280 KB Output is correct
20 Correct 5 ms 1280 KB Output is correct

Subtask #4
49.0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 256 KB Output is correct
2 Correct 2 ms 384 KB Output is correct
3 Correct 2 ms 384 KB Output is correct
4 Correct 2 ms 512 KB Output is correct
5 Correct 3 ms 512 KB Output is correct
6 Correct 2 ms 512 KB Output is correct
7 Correct 2 ms 512 KB Output is correct
8 Correct 2 ms 512 KB Output is correct
9 Correct 2 ms 512 KB Output is correct
10 Correct 4 ms 512 KB Output is correct
11 Correct 2 ms 512 KB Output is correct
12 Correct 4 ms 1280 KB Output is correct
13 Correct 4 ms 1152 KB Output is correct
14 Correct 7 ms 1280 KB Output is correct
15 Correct 5 ms 1280 KB Output is correct
16 Correct 5 ms 1280 KB Output is correct
17 Correct 4 ms 1324 KB Output is correct
18 Correct 3 ms 1152 KB Output is correct
19 Correct 3 ms 1280 KB Output is correct
20 Correct 5 ms 1280 KB Output is correct
21 Correct 13 ms 4864 KB Output is correct
22 Correct 13 ms 5248 KB Output is correct
23 Correct 14 ms 5888 KB Output is correct
24 Correct 73 ms 21240 KB Output is correct
25 Correct 83 ms 21240 KB Output is correct
26 Correct 98 ms 21240 KB Output is correct
27 Correct 76 ms 21096 KB Output is correct
28 Correct 51 ms 15352 KB Output is correct