Merge pull request #4947 from CryoJS/patch5

Python Sol for Hamiltonian Flights in DP Bitmasks Module

content/4_Gold/DP_Bitmasks.mdx

@@ -124,6 +124,55 @@ int main() {
 ```
 
 </CPPSection>
+<PySection>
+
+<Warning>
+
+Due to Python's large constant factor, the solution below TLEs.
+
+</Warning>
+
+```py
+import sys
+
+MOD = 10**9 + 7
+
+input = sys.stdin.readline
+
+n, m = map(int, input().strip().split())
+dp = [[0 for _ in range(n)] for _ in range(1 << n)]
+dp[1][0] = 1
+
+adj = [[] for _ in range(n)]
+for i in range(m):
+	a, b = map(int, input().strip().split())
+	adj[b - 1].append(a - 1)
+
+for cities in range(1, 1 << n):
+	# only consider cities that include the first city
+	if not cities & 1:
+		continue
+
+	# only consider subsets with the last city if it's the full subset
+	if cities & (1 << n - 1) and cities != (1 << n) - 1:
+		continue
+
+	# loop through possible ending cities
+	for end in range(1, n):
+		if not cities & (1 << end):
+			continue
+
+		prev_cities = cities ^ (1 << end)
+		for prev_end in adj[end]:
+			if not prev_cities & (1 << prev_end):
+				continue
+			dp[cities][end] += dp[prev_cities][prev_end]
+			dp[cities][end] %= MOD
+
+print(dp[(1 << n) - 1][n - 1])
+```
+
+</PySection>
 
 </LanguageSection>