APAC 2016 Explanation

README.md

@@ -1,7 +1,7 @@
 # Codejam
 Codejam, apac, kickstart, I/O for Women...  2017, 2016, 2015, 2014...  
 https://code.google.com/codejam/past-contests  
-ALL JAVA SOLUTIONS HERE!
+ALL EXPLANATIONS AND JAVA SOLUTIONS HERE!
 
 ## Contest List
 

apac/2016/Practice Round/A.java

@@ -1,6 +1,10 @@
 import java.io.PrintStream;
 import java.util.*;
 
+/**
+ * APAC 2016 Practice Round Problem A: Bad Horse
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/Practice Round/B.java

@@ -1,6 +1,10 @@
 import java.io.PrintStream;
 import java.util.*;
 
+/**
+ * APAC 2016 Practice Round Problem B: Captain Hammer
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/Practice Round/C.java

@@ -1,6 +1,10 @@
 import java.io.PrintStream;
 import java.util.*;
 
+/**
+ * APAC 2016 Practice Round Problem C: Moist
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/Practice Round/README.md

@@ -0,0 +1,14 @@
+# APAC 2016 Practice Round
+https://code.google.com/codejam/contest/6234486/dashboard
+
+## Problem A: Bad Horse
+
+BFS/DFS to mark color for each horse. Simple.
+
+## Problem B: Captain Hammer
+
+`t=d/v_x=2*v_y/g, ¦È=arcsin(gd/v^2)/2`
+
+## Problem C: Moist
+
+Simple. Keep the current max value.

apac/2016/RoundA/A.java

@@ -3,6 +3,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+/**
+ * APAC 2016 Round A Problem A: Googol String
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundA/B.java

@@ -3,6 +3,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+/**
+ * APAC 2016 Round A Problem B: gCube
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundA/C.java

@@ -3,6 +3,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+/**
+ * APAC 2016 Round A Problem C: gCampus
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundA/D.java

@@ -3,6 +3,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+/**
+ * APAC 2016 Round A Problem D: gSnake
+ * Check README.md for explanation.
+ */
 public class Main {
 
 

apac/2016/RoundA/README.md

@@ -0,0 +1,22 @@
+# APAC 2016 Round A
+https://code.google.com/codejam/contest/4284486/dashboard
+
+## Problem A: Googol String
+
+Simple. Nothin to tell.
+
+## Problem B: gCube
+
+Simple. `V=PI_(i,l,r) {a[i]}, Edge=pow(V, 1/d).`
+
+## Problem C: gCampus
+
+Floyd to calculate the distance of any two offices.  
+Then, for each road, if the distance between its two verticals is smaller than
+its length, then it's an inefficient road.
+
+## Problem D: gSnake
+
+Brute force. As X<=1000000, we can simulate at most 1100000 seconds.  
+for every second in [1, 1100000], check if the snake will die, or it can eat food.  
+Using HashSet to remember all bodies, and all foods eaten.

apac/2016/RoundB/A.java

@@ -3,6 +3,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+/**
+ * APAC 2016 Round B Problem A: Travel
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundB/B.java

@@ -3,6 +3,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+/**
+ * APAC 2016 Round B Problem B: gWheels
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundB/C.java

@@ -3,6 +3,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+/**
+ * APAC 2016 Round B Problem C: gNumbers
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundB/D.java

@@ -3,6 +3,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+/**
+ * APAC 2016 Round B Problem D: Albocede DNA
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {
@@ -11,10 +15,10 @@ private String solve(Scanner scanner) {
         long mod=1000000007;
         long[][][][] dp=new long[len+1][len/2+3][len/2+3][2];
         dp[0][0][0][0]=1;
-        for (int i=1;i<=len;i++) { // 长度
-            for (int j=0;j<=len/2;j++) { // a数量
-                for (int k=0;k<=len/2;k++) { // b数量
-                    for (int l=0;l<2;l++) { // 是否开始处理c或d
+        for (int i=1;i<=len;i++) { // current chracter
+            for (int j=0;j<=len/2;j++) { // number of a
+                for (int k=0;k<=len/2;k++) { // number of b
+                    for (int l=0;l<2;l++) { // whether to deal with c/d
                         if (s.charAt(i-1)=='a') {
                             if (k==0) {
                                 dp[i][j+1][k][0]+=dp[i-1][j][k][l];

apac/2016/RoundB/README.md

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+# APAC 2016 Round B
+https://code.google.com/codejam/contest/10214486/dashboard
+
+## Problem A: Travel
+
+As `Cost[t] ¡Ü Cost[t+1]+1`, we cannot stop at any city.  
+So, just for each start time, bfs to find the minimal time.
+
+## Problem B: gWheels
+
+As `p/e*e'/t=P/Q`, we can calculate all possible `e/e'` in the extra
+gears. Then, for each p in Np and t in Nt, check if Pt/pQ is possible.
+
+## Problem C: gNumbers
+
+Calculate all factors of n with only one prime. `9075=3*25*121, etc.`  
+Then dfs with memorization to solve it!
+
+## Problem D: Albocede DNA
+
+It's a really, really difficult problem.  
+DP, dp[i][j][k][l] where i means the current character, j means
+the number of a, k means the number of b, and l means if we have
+started to deal with c/d.  
+Check [D.java](D.java) for more details.
+

apac/2016/RoundC/A.java

@@ -2,6 +2,10 @@
 import java.util.*;
 import java.util.stream.Collectors;
 
+/**
+ * APAC 2016 Round C Problem A: gRanks
+ * Check README.md for explanation.
+ */
 public class Main {
 
     class Athlete {

apac/2016/RoundC/B.java

@@ -2,6 +2,10 @@
 import java.util.*;
 import java.util.stream.Collectors;
 
+/**
+ * APAC 2016 Round C Problem B: gFiles
+ * Check README.md for explanation.
+ */
 public class Main {
 
     public String solve(Scanner scanner) {

apac/2016/RoundC/C.java

@@ -2,6 +2,10 @@
 import java.util.*;
 import java.util.stream.Collectors;
 
+/**
+ * APAC 2016 Round C Problem C: gGames
+ * Check README.md for explanation.
+ */
 public class Main {
 
     public String solve(Scanner scanner) {

apac/2016/RoundC/D.java

@@ -2,6 +2,10 @@
 import java.util.*;
 import java.util.stream.Collectors;
 
+/**
+ * APAC 2016 Round C Problem D: gMatrix
+ * Check README.md for explanation.
+ */
 public class Main {
 
     public String solve(Scanner scanner) {

apac/2016/RoundC/README.md

@@ -0,0 +1,25 @@
+# APAC 2016 Round C
+https://code.google.com/codejam/contest/4284487/dashboard
+
+## Problem A: gRanks
+
+Brute force. Simple.
+
+## Problem B: gFiles
+
+Intervals intersection.  
+Take care of p=0 and p=100. Use `long` instead of `double`.
+
+## Problem C: gGames
+
+DP/DFS with memorization.  
+dp[i][x] means, can we put x in first i rounds. Here x records people
+(one in a bit).  
+To solve this, just break x into two numbers y and z, then check dp[i-1][y]
+and dp[i-1][z]. Check all possible subsets.  
+Return `dp[n][(1<<n)-1]`.
+
+## Problem D: gMatrix
+
+First, solve the problem [Sliding Window Maximum](https://leetcode.com/problems/sliding-window-maximum/).  
+Then, just apply it to each row, then each col. 

apac/2016/RoundD/A.java

@@ -2,6 +2,10 @@
 import java.util.*;
 import java.util.stream.Collectors;
 
+/**
+ * APAC 2016 Round D Problem A: Dynamic Grid
+ * Check README.md for explanation.
+ */
 public class Main {
 
     public String solve(Scanner scanner) {

apac/2016/RoundD/B.java

@@ -2,6 +2,10 @@
 import java.util.*;
 import java.util.stream.Collectors;
 
+/**
+ * APAC 2016 Round D Problem B: gBalloon
+ * Check README.md for explanation.
+ */
 public class Main {
 
     public String solve(Scanner scanner) {

apac/2016/RoundD/C.java

@@ -2,6 +2,10 @@
 import java.util.*;
 import java.util.stream.Collectors;
 
+/**
+ * APAC 2016 Round D Problem C: IP Address Summarization
+ * Check README.md for explanation.
+ */
 public class Main {
 
     class Trie {

apac/2016/RoundD/D.java

@@ -1,6 +1,10 @@
 import java.io.PrintStream;
 import java.util.*;
 
+/**
+ * APAC 2016 Round D Problem D: Virtual Rabbit
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundD/README.md

@@ -0,0 +1,40 @@
+# APAC 2016 Round D
+https://code.google.com/codejam/contest/11214486/dashboard
+
+## Problem A: Dynamic Grid
+
+Simple problem.  
+For each query, just bfs is enough.
+
+## Problem B: gBalloon
+
+Solution #1: DP  
+dp[i][j] means the minimal time of first i balloons with j amounts of energy.  
+`dp[i][j]=min(max(dp[i-1][j-|h[i]-k|], |p[i]/wind[k]|)) for 1<=k<=m`.  
+Time complexity: O(mnq)~10^9, large solved in 164.685s.  
+
+Solution #2: Binary Search
+For each time, check if we can collect all balloons.  
+Time complexity: O(mn*log(p_max)), large solved in 1.175s
+
+## Problem C: IP Address Summarization
+
+Trie. For each node in trie, mark if it's an end.  
+If a node is end, remove all sub-trees of it.  
+If the left and right children of a node are both end, then it's an end.
+
+## Problem D: Virtual Rabbit
+
+For small, just check if `[curr+1, curr+x]` has intersection with
+`[day_start+g, dat_start+w-1], [day_start+h, day_start+b-1],
+[day_start+86400+g, dat_start+86400+w-1], [day_start+86400+h,
+day_start+86400+b-1]`.  
+Find the max point to be the fed time.
+
+For large, we cannot simulate in the whole process.  
+What's to do is, find the loop. That is, find two days where
+Alice feed the rabbit at the same second.  
+After finding the loop, we can just calculate how many days in a loop,
+how many feed times in a loop, and how many loops there are.  
+It's hard to implement, please be careful.  
+Check [D.java](D.java) for more details.

apac/2016/RoundE/A.java

@@ -1,6 +1,10 @@
 import java.io.PrintStream;
 import java.util.*;
 
+/**
+ * APAC 2016 Round E Problem A: Lazy Spelling Bee
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundE/B.java

@@ -1,6 +1,10 @@
 import java.io.PrintStream;
 import java.util.*;
 
+/**
+ * APAC 2016 Round E Problem B: Robot Rock Band
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {

apac/2016/RoundE/C.java

@@ -1,6 +1,10 @@
 import java.io.PrintStream;
 import java.util.*;
 
+/**
+ * APAC 2016 Round E Problem C: Not So Random
+ * Check README.md for explanation.
+ */
 public class Main {
 
     private String solve(Scanner scanner) {