Merge branch 'smv1999:master' into patch-1

Author: madihamallick

Arrays/trappingrainwater.cpp

@@ -0,0 +1,29 @@
+// Given an array of numbers which are heights to the container, we need to find upto what maximum value water can be filled in this vessel
+// of different heights.
+// Time complexity - O(n)
+//Space complexity - O(1)
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+    int arr[]={1,8,6,2,5,4,8,3,7}; //array of diff heights
+    int l=0,n=sizeof(arr)/sizeof(int),r=n-1;
+    int max_area=0,h,a,b;
+    //2 pointers algorithm
+
+    while(l<r){ 
+        h=min(arr[l],arr[r]); //choosing the minimum of both heights -left and right side
+        b=r-l; //base = right height index - left 
+        a=h*b;
+        max_area=max(a,max_area); //idea to maximize the area to trap more water
+        if(arr[l]<=arr[r]){
+            l++; //if right ride height is greater move left pointer to choose max of heights
+        }
+        else{
+            r--; //else move right pointer to choose next max height
+        }
+    }
+    cout<<"Maximum water that can be trapped is : "<<max_area;
+    return 0;
+
+}

Backtracking/Knight's_Tour.java

@@ -0,0 +1,65 @@
+/*Moving according to the rules of chess knight must visit each square exactly once. Print the order of each the cell in which they are visited.*/
+import java.util.*;
+public class MyClass {
+    public static void main(String args[]) {
+        Scanner sc = new Scanner(System.in);
+        int n = sc.nextInt();
+        // provide start position
+        int r = sc.nextInt();
+        int c = sc.nextInt();
+        int board[][] = new int[n][n];
+        // The 8 possible moves where a knight can move from its current position
+        int posx[] = {-1,-1,1,1,-2,-2,2,2};
+        int posy[] = {-2,2,-2,2,-1,1,-1,1};
+        path(board, r, c, 1, posx, posy);
+    }
+    public static boolean path(int board[][], int row, int col, int move, int posx[], int posy[]) {
+        board[row][col] = move;
+        // if all the positions are visited then print the result
+        if (move == board.length*board.length) {
+            // printing result in matrix form
+            for (int i = 0; i < board.length; i++) {
+                for (int j = 0; j < board.length; j++)
+                    if (board[i][j] < 10)
+                        System.out.print("0" + board[i][j] + " ");
+                    else
+                        System.out.print(board[i][j] + " ");
+                System.out.println();
+            }
+            return true;
+        }
+        for (int i = 0; i < 8; i++) {
+            int newx = row + posx[i];
+            int newy = col + posy[i];
+            // checking if the new position is a valid move and not visited yet
+            if (validmove(newx, newy, board) && board[newx][newy] == 0) {
+                if (path(board, newx, newy, move + 1, posx, posy)) {
+                    return true;
+                }
+            }
+        }
+        // if position is not valid mark position as unvisited in the matrix
+        board[row][col] = 0;
+        return false;
+    }
+    // checks that the new position is not outside the matrix of n*n
+    static boolean validmove(int newx, int newy, int board[][]) {
+        if (newx >= 0 && newx < board.length && newy >= 0 && newy < board.length)
+            return true;
+        return false;
+    }
+}
+
+/*Input
+8
+0 
+0
+Output
+01 08 15 22 03 10 19 64 
+16 23 02 09 18 21 04 11 
+07 14 17 24 05 12 63 20 
+34 25 06 13 44 27 52 61 
+55 46 33 26 53 62 43 28 
+32 35 54 45 40 29 60 51 
+47 56 37 30 49 58 39 42 
+36 31 48 57 38 41 50 59 */

Backtracking/N-Queen Problem.cpp

@@ -0,0 +1,108 @@
+/* N-Queen Problem
+
+
+You have to place n queens on an nxn chessboard.
+Idea: Try all the possible positions for the queen. isSafe functions check whether
+the current position is safe or not
+
+*/
+
+#include<iostream>
+using namespace std;
+
+	
+bool isSafe(int board[][10], int i, int j, int n){
+	//Check in col
+		
+	for(int row=0;row<i;row++){
+		if(board[row][j] == 1){
+			return false;
+		}
+	}
+	//Left diagonal
+	int x=i;
+	int y=j;
+		
+	while(x>=0 && y>=0){
+		if(board[x][y]==1){
+			return false;
+		}
+		x--;
+		y--;
+	}
+	//Right diagonal
+	x=i;
+	y=j;
+		
+	while(x>=0 && y>=0){
+		if(board[x][y]==1){
+			return false;
+		}
+		x--;
+		y++;
+	}
+	//The position is safe
+	return true;
+	
+	
+}
+
+bool nQueen(int board[][10], int i,int n){
+	if(i==n){//base case
+	// Place Queeen in n rows (0..n-1)
+	//print the board
+	for(int i=0;i<n;i++){
+		for(int j=0;j<n;j++){
+			if(board[i][j]==1){
+				cout<<"Q ";
+			}
+			else{
+				cout<<"_ ";
+			}
+		}
+		cout<<endl;
+	}
+		return true;
+	}
+	//Recursive case
+	
+	for(int j=0;j<n;j++){
+		//Check i,j th position is safe to place the queen or not.
+		if(isSafe(board,i,j,n)){
+			//Place the Queen ,i, j in the right position
+			board[i][j]=1;
+			
+			if(nQueen(board,i+1,n)){
+				return true;
+			}
+			//Means i,j is not the right position
+			board[i][j]=0; //backtracking
+		}
+	}
+	//coudln't place the queen in current position.
+	return false;
+}
+		
+	
+int main(){
+	int n;
+	cin>>n;
+	
+	int board[10][10]={0};
+	nQueen(board,0,n);
+	
+	return 0;
+	
+}
+
+/* Input:
+4
+
+Output:
+
+_ Q _ _
+_ _ _ Q
+Q _ _ _
+_ _ Q _
+
+*/

Codechef Problems/DSA Learning Series/Alternative Square Pattern.java

@@ -0,0 +1,64 @@
+/* You're given a number N. Print the first N lines of the below-given pattern.
+
+1 2 3 4 5
+10 9 8 7 6
+11 12 13 14 15
+20 19 18 17 16
+21 22 23 24 25
+30 29 28 27 26
+Input:
+First-line will contain the number N.
+Output:
+Print the first N lines of the given pattern.
+
+Constraints
+1≤N≤200
+Sample Input 1:
+4
+Sample Output 1:
+1 2 3 4 5
+10 9 8 7 6
+11 12 13 14 15
+20 19 18 17 16
+Sample Input 2:
+2
+Sample Output 2:
+1 2 3 4 5
+10 9 8 7 6
+EXPLANATION:
+In the first example, we'll print the first 4 lines of the given pattern.
+In the second example, we'll print the first 2 lines of the given pattern. */
+
+import java.util.*;
+import java.lang.*;
+import java.io.*;
+
+/* Name of the class has to be "Main" only if the class is public. */
+class Codechef
+{
+	public static void main (String[] args) throws java.lang.Exception
+	{
+		Scanner sc= new Scanner(System.in);
+		int n= sc.nextInt();
+		for (int i=1; i<=n; i++)
+		{
+		    if(i%2!=0)
+		    {
+		        for(int j=(5*(i-1)+1);j<=(5*i);j++)
+		        {
+		            System.out.print(j+" ");
+		        }
+		         System.out.println();
+		    }
+		    else{
+		        for(int j=(5*i);j>=(5*(i-1)+1);j--)
+		    {
+		            System.out.print(j+" ");
+		    }
+		     System.out.println();
+		    }
+		   
+		    
+		}
+	}
+}

Codechef Problems/DSA Learning Series/Buy Please.c

@@ -0,0 +1,36 @@
+/* Chef went to a shop and buys a pens and b pencils. Each pen costs x units and each pencil costs y units. Now find what is the total amount Chef will spend to buy a pens and b pencils.
+
+Input:
+First-line will contain 4 space separated integers a, b, x and y respectively.
+Output:
+Print the answer in a new line.
+
+Constraints
+1≤a,b,x,y≤103
+Sample Input 1:
+2 4 4 5
+Sample Output 1:
+28
+Sample Input 2:
+1 1 4 8
+Sample Output 2:
+12
+EXPLANATION:
+In the first example, total cost is (2 * 4 + 4 * 5) = 28.
+In the second example, total cost is (1 * 4 + 1 * 8) = 12.  */
+
+
+#include <stdio.h>
+
+int main(void) {
+	
+	int a,b,x,y;
+	scanf("%d %d %d %d",&a,&b,&x,&y);
+	int pen_cost= a*x;
+	int pencil_cost=b*y;
+	int total=pen_cost+pencil_cost;
+	printf("%d",total);
+	
+	return 0;
+	
+}

Codechef Problems/DSA Learning Series/Factors Finding.c

@@ -0,0 +1,48 @@
+/* You are given a number N and find all the distinct factors of N.
+
+Input:
+First-line will contain the number N.
+Output:
+In the first line print number of distinct factors of N.
+In the second line print all distinct factors in ascending order separated by space.
+Constraints
+1≤N≤106
+Sample Input 1:
+4
+Sample Output 1:
+3
+1 2 4
+Sample Input 2:
+6
+Sample Output 2:
+4
+1 2 3 6
+EXPLANATION:
+In the first example, all factors of 4 are 1, 2, 4.
+In the second example, all factors of 6 are 1, 2, 3, 6. */
+
+#include <stdio.h>
+
+int main(void) {
+	
+	int n;
+	scanf("%d",&n);
+	int c=0;
+	int a[n];
+	
+	for(int i=1;i<=n;i++)
+	{
+	    if(n%i==0)
+	    {
+	        a[c]=i;
+	        c++;
+	    }
+	}
+	printf("%d \n",c);
+		for(int i=0;i<c;i++)
+		{
+		    printf("%d ",a[i]);
+		}
+	
+	return 0;
+}