Hello, I am currently doing this question: https://codeforces.net/contest/837/problem/D↵
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And I need some help. I came up with a good dp algorithm myself:↵
↵
dp[i][j][k] means the maximum exponent of prime factor 2 we can achieve when we:↵
↵
1. choose from the first i integers in a↵
↵
2. choose a subset of length j from the first i integers↵
↵
3. the exponent of 5 is at most k↵
↵
then, dp[i][j][k] = max(dp[i-1][j][k], dp[i-1][j-1][k-cur_exp5] + cur_exp2)↵
↵
note dp[0][0][0] = 0 (don't have to initialize anything)↵
↵
And implemented this algorithm in Python:↵
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n, K = map(int, input().split())↵
a = list(map(int, input().split()))↵
↵
def factors(x):↵
cnt2, cnt5 = 0, 0↵
while x % 5 == 0:↵
x //= 5↵
cnt5 += 1↵
while x % 2 == 0:↵
x //= 2↵
cnt2 += 1↵
return [cnt2, cnt5]↵
↵
b = []↵
mc = []↵
for A in a:↵
c2, c5 = factors(A)↵
b.append([c2, c5])↵
mc.append(c5)↵
mc.sort(reverse=True)↵
MAX_CNT5 = sum(mc[:K])↵
↵
dp = [[[0 for _ in range(MAX_CNT5+1)] for _ in range(K+1)] for _ in range(n+1)]↵
↵
for i in range(1, n+1):↵
for j in range(1, K+1):↵
for k in range(MAX_CNT5+1):↵
if k >= b[i-1][1]:↵
dp[i][j][k] = max(dp[i-1][j][k],↵
dp[i-1][j-1][k-b[i-1][1]] + b[i-1][0])↵
else:↵
dp[i][j][k] = dp[i-1][j][k]↵
↵
ans = 0↵
for i in range(len(dp[n][K])):↵
ans = max(ans, min(i, dp[n][K][i]))↵
↵
print(ans)[submission:274520784]↵
↵
↵
However, this code WAs for test case 8, with my answer of 11 being higher than the expected answer of 9.↵
I have read the editorial for this question, and I believe the DP formula in the editorial is the same as my DP formula mentioned above (please correct me if I am wrong). Therefore, because I believe I have the DP formula correct, I am really confused on why this code still WAs.↵
I know asking people to debug a code is sometimes annoying but I really tried everything and could not figure out why this code is not working, and I would really appreciate it if anyone could tell me why. ↵
↵
↵
Thank you so much!↵
↵
↵
And I need some help. I came up with a good dp algorithm myself:↵
↵
dp[i][j][k] means the maximum exponent of prime factor 2 we can achieve when we:↵
↵
1. choose from the first i integers in a↵
↵
2. choose a subset of length j from the first i integers↵
↵
3. the exponent of 5 is at most k↵
↵
then, dp[i][j][k] = max(dp[i-1][j][k], dp[i-1][j-1][k-cur_exp5] + cur_exp2)↵
↵
note dp[0][0][0] = 0 (don't have to initialize anything)↵
↵
And implemented this algorithm in Python:↵
↵
a = list(map(int, input().split()))↵
↵
def factors(x):↵
cnt2, cnt5 = 0, 0↵
while x % 5 == 0:↵
x //= 5↵
cnt5 += 1↵
while x % 2 == 0:↵
x //= 2↵
cnt2 += 1↵
return [cnt2, cnt5]↵
↵
b = []↵
mc = []↵
for A in a:↵
c2, c5 = factors(A)↵
b.append([c2, c5])↵
mc.append(c5)↵
mc.sort(reverse=True)↵
MAX_CNT5 = sum(mc[:K])↵
↵
dp = [[[0 for _ in range(MAX_CNT5+1)] for _ in range(K+1)] for _ in range(n+1)]↵
↵
for i in range(1, n+1):↵
for j in range(1, K+1):↵
for k in range(MAX_CNT5+1):↵
if k >= b[i-1][1]:↵
dp[i][j][k] = max(dp[i-1][j][k],↵
dp[i-1][j-1][k-b[i-1][1]] + b[i-1][0])↵
else:↵
dp[i][j][k] = dp[i-1][j][k]↵
↵
ans = 0↵
for i in range(len(dp[n][K])):↵
ans = max(ans, min(i, dp[n][K][i]))↵
↵
print(ans)
↵
↵
However, this code WAs for test case 8, with my answer of 11 being higher than the expected answer of 9.↵
I have read the editorial for this question, and I believe the DP formula in the editorial is the same as my DP formula mentioned above (please correct me if I am wrong). Therefore, because I believe I have the DP formula correct, I am really confused on why this code still WAs.↵
I know asking people to debug a code is sometimes annoying but I really tried everything and could not figure out why this code is not working, and I would really appreciate it if anyone could tell me why. ↵
↵
↵
Thank you so much!↵
↵
