Add ECPC 2017 solutions

Codeforces/259A.py

@@ -0,0 +1,10 @@
+#AC
+import re
+
+for i in range(8):
+    s = input()
+    if re.findall(r'(WW)|(BB)', s):
+        print('NO')
+        exit(0)
+
+print('YES')

Codeforces/CF101840-GYM-A.cpp

@@ -0,0 +1,110 @@
+// ECPC 2017
+// AC
+
+#include<bits/stdc++.h>
+using namespace std;
+
+int N;
+long double p;
+int x,y,k;
+
+long double dp[50][50][3001];
+int vis[50][50][3001];
+int t;
+
+bool valid_move(int pos_x, int pos_y)
+{
+	if (pos_x < 0 || pos_y < 0 || pos_x == N || pos_y == N || pos_x==pos_y)
+		return 0;
+	return 1;	
+}
+
+long double solve(int pos_x, int pos_y, int rem_r)
+{
+	if (pos_x < 0 || pos_y < 0 || pos_x == N || pos_y == N || pos_x==pos_y)
+		return 0;
+	if (vis[pos_x][pos_y][rem_r] == t)
+		return dp[pos_x][pos_y][rem_r];
+
+	vis[pos_x][pos_y][rem_r] = t;
+	if (rem_r == 0)
+	{
+		if (pos_x == x && pos_y == y)
+			return dp[pos_x][pos_y][rem_r] = 1;
+		return dp[pos_x][pos_y][rem_r] = 0;
+	}
+	// probability of each pair = 1 / nC2
+	long double prob_round = 1.0 / (N-1); 
+	long double ans = (1-p) * solve(pos_x, pos_y, rem_r -1);
+	int valid_moves = 0;
+
+	if (abs(pos_x-pos_y) == 1)
+	{
+		// adjancent
+		ans += prob_round * p * solve(pos_y, pos_x, rem_r - 1);
+		if (valid_move(pos_y, pos_x))
+			valid_moves ++;
+	}
+	ans += prob_round * p * solve(pos_x-1, pos_y, rem_r - 1);
+	ans += prob_round * p * solve(pos_x+1, pos_y, rem_r - 1);
+	ans += prob_round * p * solve(pos_x, pos_y-1, rem_r - 1);
+	ans += prob_round * p * solve(pos_x, pos_y+1, rem_r - 1);
+
+	int dx []= {-1, 1, 0, 0};
+	int dy []= {0, 0, -1, 1};
+	for (int i=0;i<4;i++)
+	{
+		if (valid_move(pos_x+dx[i], pos_y+dy[i]))
+			valid_moves++;
+	}
+	// Prob of same location = ??
+
+	ans += (N-1- valid_moves) * prob_round * p * solve(pos_x, pos_y, rem_r - 1);
+	return dp[pos_x][pos_y][rem_r] = ans;
+}
+
+long double dp_1[50][3001];
+int vis_1[50][3001];
+
+long double solve_1(int pos_x, int rem_r)
+{
+	if (pos_x <0 || pos_x == N)
+		return 0;
+	if (vis_1[pos_x][rem_r] == t)
+		return dp_1[pos_x][rem_r];
+	if (rem_r == 0)
+	{
+		return dp_1[pos_x][rem_r] = (pos_x == x);
+	}
+	vis_1[pos_x][rem_r] = t;
+	long double ans = (1-p) * solve_1(pos_x, rem_r -1);;
+	long double prob_round = 1.0 / (N-1); 
+	ans += prob_round * p * solve_1(pos_x - 1, rem_r - 1);
+	ans += prob_round * p * solve_1(pos_x + 1, rem_r - 1);
+	if (pos_x == 0 || pos_x == N-1)
+		ans += (N-2) * prob_round * p * solve_1(pos_x, rem_r - 1);
+	else
+		ans += (N-3) * prob_round * p * solve_1(pos_x, rem_r - 1);
+	return dp_1[pos_x][rem_r] = ans;
+}
+int main()
+{
+	int T;
+	freopen("in.txt", "r", stdin);
+	cin>>T;
+	for (t=1;t<=T;t++)
+	{
+		cin>>N>>p>>x>>y>>k;
+
+		long double ans = 1;
+		if (N==1)
+			ans = 1;
+		else if (x==y)
+			ans = solve_1(x, k);
+		else
+			ans = solve(y, x, k);
+		printf("Case %d: %0.5LF\n", t, ans);
+		// cout<<fixed<<setprecision(5)<<solve<<"\n";
+	}
+
+}

Codeforces/ECPC2017_G.cpp → Codeforces/CF101840-GYM-G.cpp

@@ -1,3 +1,4 @@
+// AC
 #include "bits/stdc++.h"
 using namespace std;
 #define PI (2*acos(0))
@@ -11,9 +12,7 @@ Case 3: 31096.23444
 
 int main()
 {
-	#ifndef ONLINE_JUDGE
-		freopen("in.txt","r",stdin);
-	#endif
+	freopen("glorious.in","r",stdin);
 	int T;
 	cin>>T;
 	for (int t=1;t<=T;t++)
@@ -30,4 +29,4 @@ int main()
 		ans *= S;
 		printf("Case %d: %0.5LF\n", t,ans);
 	}
-}
+}

SPOJ/LOOPEXP.cpp

@@ -0,0 +1,28 @@
+/* AC
+- The position of the maximum number is important.
+- Linearity of expectation.
+*/
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int main()
+{
+	long double dp[100001];
+	dp[0] = 0;
+	long double ans = 0;
+	for (int n=1;n<=100000;n++)
+	{
+		dp [n] = (ans/n) + 1;
+		ans += dp[n];
+	}
+
+	int t;
+	cin>>t;
+	while(t--)
+	{
+		int n;
+		cin>>n;
+		cout<<fixed<<setprecision(9)<<dp[n]<<"\n";
+	}
+}