Create bit.java

Author: tarun11Mavani

Data Structures/Fenwick_tree/bit.java

@@ -0,0 +1,249 @@
+import java.util.*;
+import java.awt.List;
+import java.io.*;
+import java.lang.*;
+import java.lang.reflect.Array;
+
+public class code8 {
+
+	
+	
+	public static void main(String[] args) {
+		InputReader in = new InputReader(System.in);
+		PrintWriter pw = new PrintWriter(System.out);
+
+		// Code starts..
+
+		int n = in.nextInt();
+		int[] a = in.nextIntArray(n);
+		query[] qr1 = new query[n];
+		pair[] p = new pair[n];
+		q = n;
+		HashMap<Integer, Integer> map = new HashMap<>();
+		for(int i=0; i<n; i++)
+			map.put(a[i],i);
+		Arrays.sort(a);
+		for(int i=n-1; i>=0; i--)
+		{
+			p[n-i-1] = new pair(-a[i], map.get(a[i])); 
+			int l = 0;
+			int r = map.get(a[i])-1;
+			int x = a[i];
+			qr1[n-i-1] = new query(l, r, -a[i], map.get(a[i]));
+			//  pw.println(qr1[n-i-1].l+" "+qr1[n-i-1].x+" "+p[n-i-1]);
+				
+		}
+		
+		int[] ans = answerQueries(n, qr1, q, p);
+			
+		for(int i=0; i<n; i++)
+		{
+			int l = map.get(a[i])+1;
+        	int r = n-1;
+        	int x = a[i];
+        	qr1[i].l = l;
+        	qr1[i].r = r;
+        	qr1[i].x = x;
+        	qr1[i].idx = map.get(a[i]);
+        	
+          	p[i].x = x;
+          	p[i].y = map.get(a[i]);
+        //    pw.println(qr1[i].l+" "+qr1[i].x+" "+p[i]+" ");
+			
+		}
+	
+	
+		
+		int[] ans2 = answerQueries(n, qr1, q, p);
+		long sum = 0;
+		for(int i=0; i<q; i++)
+		{
+			sum += (long)ans[i]*ans2[i];
+			//pw.println(ans[i]+" "+ans2[i]);
+		}
+		
+		
+		pw.print(sum);
+		// code ends...
+
+		pw.flush();
+		pw.close();
+	}
+
+	
+	
+	public static void update(int bit[], int idx, int val, int n) {
+	
+		
+		for(; idx<=n; idx+= (idx&-idx))
+			bit[idx] += val;
+	}
+	
+	    
+	
+	public static int query(int bit[], int idx, int n) {
+		int sum = 0;
+		for (; idx > 0; idx -= idx&-idx)
+	        sum += bit[idx];
+		return sum;
+	}
+	
+	
+	
+	public static int[] answerQueries(int n, query[] qr, int q,
+            pair[] p)
+
+	{
+
+		int[] bit = new int[n+1];
+		/*p = suffle(p, new Random());
+		qr = suffle(qr, new Random());
+		
+		//Arrays.sort(p);
+		Arrays.sort(qr);
+		*/
+		int curr = 0;
+		int[] ans = new int[q];
+		for (int i=0; i<q; i++)
+		{
+			//System.out.println(p[curr]+" "+i+" "+curr);
+			if(curr<n)
+			while (p[curr].x <= qr[i].x && curr<n)
+			{
+					update(bit, p[curr].y+1, 1, n);
+					curr++;
+					if(curr==n)
+						break;
+			}
+		
+			ans[qr[i].idx] = query(bit, qr[i].r+1, n) -
+		            query(bit, qr[i].l, n);
+		}
+
+		return ans;
+
+		
+}
+	
+	
+	
+	
+
+	static class InputReader
+	{
+
+		private final InputStream stream;
+		private final byte[] buf = new byte[8192];
+		private int curChar, snumChars;
+		private SpaceCharFilter filter;
+
+		public InputReader(InputStream stream) {
+			this.stream = stream;
+		}
+
+		public int snext() {
+			if (snumChars == -1)
+				throw new InputMismatchException();
+			if (curChar >= snumChars) {
+				curChar = 0;
+				try {
+					snumChars = stream.read(buf);
+				} catch (IOException e) {
+					throw new InputMismatchException();
+				}
+				if (snumChars <= 0)
+					return -1;
+			}
+			return buf[curChar++];
+		}
+
+		public int nextInt() {
+			int c = snext();
+			while (isSpaceChar(c)) {
+				c = snext();
+			}
+			int sgn = 1;
+			if (c == '-') {
+				sgn = -1;
+				c = snext();
+			}
+			int res = 0;
+			do {
+				if (c < '0' || c > '9')
+					throw new InputMismatchException();
+				res *= 10;
+				res += c - '0';
+				c = snext();
+			} while (!isSpaceChar(c));
+			return res * sgn;
+		}
+
+		public long nextLong() {
+			int c = snext();
+			while (isSpaceChar(c)) {
+				c = snext();
+			}
+			int sgn = 1;
+			if (c == '-') {
+				sgn = -1;
+				c = snext();
+			}
+			long res = 0;
+			do {
+				if (c < '0' || c > '9')
+					throw new InputMismatchException();
+				res *= 10;
+				res += c - '0';
+				c = snext();
+			} while (!isSpaceChar(c));
+			return res * sgn;
+		}
+
+		public int[] nextIntArray(int n) {
+			int a[] = new int[n];
+			for (int i = 0; i < n; i++) {
+				a[i] = nextInt();
+			}
+			return a;
+		}
+
+		public String readString() {
+			int c = snext();
+			while (isSpaceChar(c)) {
+				c = snext();
+			}
+			StringBuilder res = new StringBuilder();
+			do {
+				res.appendCodePoint(c);
+				c = snext();
+			} while (!isSpaceChar(c));
+			return res.toString();
+		}
+
+		public String nextLine() {
+			int c = snext();
+			while (isSpaceChar(c))
+				c = snext();
+			StringBuilder res = new StringBuilder();
+			do {
+				res.appendCodePoint(c);
+				c = snext();
+			} while (!isEndOfLine(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;
+		}
+
+		private boolean isEndOfLine(int c) {
+			return c == '\n' || c == '\r' || c == -1;
+		}
+
+		public interface SpaceCharFilter {
+			public boolean isSpaceChar(int ch);
+		}
+	}
+}