Java 8 Coding challenge: Raees's Liquor Tank

Raees wants to build a new tank to hide his illegal liquor . He comes up with some designs . Now he asks you to find out maximum units of liquor he can fill in the tank.

You are given N elements , corresponding to heights of walls . See the figure for input 0 ,8 ,0 ,4 ,0 ,3 ,0 ,5 ,0 ,3 ,0 ,1 ,0.

Maximum amount of liquor that can be filled is 5 + 1 + 5 + 2 + 5 + 3 + 1 = 22.

Eg : For input 4 ,2 ,4 ,3 Output will be 2 .

INPUT

• First line of input contains a single integer N.
• Second line of input contains N non-negative integers ( A0 --- A(n-1) ).

OUTPUT

• Single integer , answer to the Raees's question.

CONSTRAINTS

• 1 <= N <= 1000
• 1 <= Ai <= 1000

SAMPLE INPUT

13
0 8 0 4 0 3 0 5 0 3 0 1 0

SAMPLE OUTPUT

22

 Code:

import java.io.*;
import java.util.*;
import java.math.*;
import java.lang.*;
import static java.lang.Math.*;
 
public class Q1
{
 
 static class InputReader
 {
 private InputStream stream;
 private byte[] buf = new byte[1024];
 private int curChar;
 private int numChars;
 private SpaceCharFilter filter;
 
 public InputReader(InputStream stream)
 {
 this.stream = stream;
 }
 
 public int read()
 {
 if (numChars==-1) 
 throw new InputMismatchException();
 
 if (curChar >= numChars)
 {
 curChar = 0;
 try 
 {
 numChars = stream.read(buf);
 }
 catch (IOException e)
 {
 throw new InputMismatchException();
 }
 
 if(numChars <= 0) 
 return -1;
 }
 return buf[curChar++];
 }
 
 public String nextLine()
 {
 BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
 String str = "";
 try
 {
 str = br.readLine();
 }
 catch (IOException e)
 {
 e.printStackTrace();
 }
 return str;
 }
 public int nextInt()
 {
 int c = read();
 
 while(isSpaceChar(c)) 
 c = read();
 
 int sgn = 1;
 
 if (c == '-') 
 {
 sgn = -1;
 c = read();
 }
 
 int res = 0;
 do 
 {
 if(c<'0'||c>'9') 
 throw new InputMismatchException();
 res *= 10;
 res += c - '0';
 c = read();
 }
 while (!isSpaceChar(c)); 
 
 return res * sgn;
 }
 
 public long nextLong() 
 {
 int c = read();
 while (isSpaceChar(c))
 c = read();
 int sgn = 1;
 if (c == '-') 
 {
 sgn = -1;
 c = read();
 }
 long res = 0;
 
 do 
 {
 if (c < '0' || c > '9')
 throw new InputMismatchException();
 res *= 10;
 res += c - '0';
 c = read();
 }
 while (!isSpaceChar(c));
 return res * sgn;
 }
 
 public double nextDouble() 
 {
 int c = read();
 while (isSpaceChar(c))
 c = read();
 int sgn = 1;
 if (c == '-') 
 {
 sgn = -1;
 c = read();
 }
 double res = 0;
 while (!isSpaceChar(c) && c != '.') 
 {
 if (c == 'e' || c == 'E')
 return res * Math.pow(10, nextInt());
 if (c < '0' || c > '9')
 throw new InputMismatchException();
 res *= 10;
 res += c - '0';
 c = read();
 }
 if (c == '.') 
 {
 c = read();
 double m = 1;
 while (!isSpaceChar(c)) 
 {
 if (c == 'e' || c == 'E')
 return res * Math.pow(10, nextInt());
 if (c < '0' || c > '9')
 throw new InputMismatchException();
 m /= 10;
 res += (c - '0') * m;
 c = read();
 }
 }
 return res * sgn;
 }
 
 public String readString() 
 {
 int c = read();
 while (isSpaceChar(c))
 c = read();
 StringBuilder res = new StringBuilder();
 do 
 {
 res.appendCodePoint(c);
 c = read();
 } 
 while (!isSpaceChar(c));
 
 return res.toString();
 }
 
 public boolean isSpaceChar(int c) 
 {
 if (filter != null)
 return filter.isSpaceChar(c);
 return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
 }
 
 public String next() 
 {
 return readString();
 }
 
 public interface SpaceCharFilter 
 {
 public boolean isSpaceChar(int ch);
 }
 }
 
 public static int[] SOE()
 {
 int n=(int)(1e5); //till which digit
 
 int ip[]=new int[n];
 
 for(int i=2;i<(int)Math.sqrt(n);i++)
 {
 if(ip[i]==0)
 {
 for(int j=i*i;j<n;j=j+i)
 {
 ip[j]++;
 }
 }
 }
 
 ip[1]++; //counts 1 and 0 as primes
 ip[0]++;
 
 return ip;
 }
 
 private static long gcd(long a, long b)
 {
 while (b > 0)
 {
 long temp = b;
 b = a % b; // % is remainder
 a = temp;
 }
 return a;
}
 
 private static long gcd(long[] input)
 {
 long result = input[0];
 
 for(int i = 1; i < input.length; i++) 
 result = gcd(result, input[i]);
 
 return result;
 }
 
 private static long lcm(long a, long b)
 {
 return a * (b / gcd(a, b));
 }
 
 private static long lcm(long[] input)
 {
 long result = input[0];
 
 for(int i = 1; i < input.length; i++) 
 result = lcm(result, input[i]);
 
 return result;
 }
 
 public static void Array_2dsort(Integer[][] a)
 {
 
 Arrays.sort(a, new Comparator<Integer[]>() {
 public int compare(Integer[] int1, Integer[] int2) {
 Integer numOfKeys1 = int1[1]; //about which column u want to sort
 Integer numOfKeys2 = int2[1];
 return numOfKeys1.compareTo(numOfKeys2);
 }
 });
 
 }
 
 
 public static boolean Square(int x)
 {
 boolean ans=false;
 
 int a=(int)Math.sqrt(x);
 
 if(a*a==x)
 ans=true;
 
 return ans;
 }
 
 public static void main(String args[]) throws Exception
 {
 InputReader in=new InputReader(System.in); 
 PrintWriter w=new PrintWriter(System.out);
 
 int n=in.nextInt();
 
 int a[]=new int[n];
 
 for(int i=0;i<n;i++)
 a[i]=in.nextInt();
 
 
 int total=0;
 int l[]=new int[n];
 int r[]=new int[n];
 l[0]=a[0];
 r[n-1]=a[n-1];
 
 for(int i=1;i<n;i++)
 l[i]=(int)Math.max(l[i-1],a[i]);
 
 for(int i=n-2;i>=0;i--)
 r[i]=(int)Math.max(r[i+1],a[i]);
 
 for(int i=0;i<n;i++)
 total+=(int)Math.min(l[i],r[i])-a[i];
 
 w.println(total);
 
 w.close(); 
 }
}