recursion advance + backtracking basics

Author: Mohit Jain

0-1Knapsack

@@ -0,0 +1,44 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+
+int profit(int N, int C, int *wt, 
+	int *prices){
+
+	if(N == 0 || C == 0) {
+		return 0;
+	}
+
+	int includeItem, excludeItem;
+	int ans = 0; 
+	includeItem = excludeItem = INT_MIN;
+    if(wt[N-1] <=C) {
+	includeItem = prices[N-1] + profit(N-1,
+		C-wt[N-1],wt,prices);
+      }
+	excludeItem = profit(N-1, C,wt,prices);
+
+	return max(includeItem,excludeItem);
+}
+
+
+int main() {
+
+  #ifndef ONLINE_JUDGE
+    // for getting input from input.txt
+    freopen("input.txt", "r", stdin);
+    // for writing output to output.txt
+    freopen("output.txt", "w", stdout);
+    #endif
+    
+    
+    int weights[] = {1,2,3,5};
+
+    int prices[] = {40,20,30,100};
+
+    int N = 4;
+    int C = 7;
+    cout<<profit(N,C,weights,prices)<<endl;
+	return 0;
+}

0-1Knapsack.cpp

@@ -0,0 +1,53 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+   bool checkSorted(int *a, int n){
+
+   	if(n == 0 or n == 1) {
+   		return true;
+   	}
+
+   	if (a[0] <= a[1] and checkSorted(a+1, n-1)) { return true; } 
+   
+     
+
+     return false;
+
+   }
+
+
+int main() {
+    
+    #ifndef ONLINE_JUDGE
+    // for getting input from input.txt
+    freopen("input.txt", "r", stdin);
+    // for writing output to output.txt
+    freopen("output.txt", "w", stdout);
+    #endif
+
+
+    int n;
+
+    cin>>n;
+
+    int a[n];
+
+    for(int i = 0; i < n ; i ++) {
+    	cin>>a[i];
+    }
+     if(checkSorted(a,n-1)) {
+     	cout<<"true"<<endl;
+
+     }
+     else {
+     	cout<<"false"<<endl;
+     }
+
+   
+
+
+
+
+	return 0;
+}

CheckSorted

@@ -0,0 +1,65 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+bool ratInMaze(char maze[10][10], int 
+	soln[][10], int i,int j,int m,int n){
+
+	if(i == m and j == n) {
+
+		soln[m][n] = 1;
+  
+    for(int i=0; i <=m; i++){
+    	for(int j =0; j <=n; j++) {
+    		cout<<soln[i][j]<< " ";
+    	}
+    	  cout<<endl;
+    }
+     cout<<endl;
+
+		return true;
+	}
+
+	// Rec case 
+	if(i > m || j >n) return false;
+
+	if(maze[i][j] == 'X') return false;
+
+	soln[i][j] = 1;
+	bool rightSide = ratInMaze(maze,soln,
+		  i,j+1,m,n);
+	bool downSide = ratInMaze(maze,soln,
+		i+1,j , m, n);
+    soln[i][j] = 0;
+	if (rightSide || downSide) return 
+		true;
+	return false;
+}
+
+int main() {
+    
+    #ifndef ONLINE_JUDGE
+    // for getting input from input.txt
+    freopen("input.txt", "r", stdin);
+    // for writing output to output.txt
+    freopen("output.txt", "w", stdout);
+    #endif
+    
+    char maze[10][10] = {
+    	       "0000",
+    	       "00X0",
+    	       "000X",
+    	       "0X00"
+    };    
+
+    
+    int soln[10][10] = {0};
+    int m = 4, n =4;
+
+    bool ans = ratInMaze(maze,soln,0,0,m-1
+    	,n-1);
+     if(!ans) {
+     	cout<< " path does not exist";
+     }
+	return 0;
+}

CheckSorted.cpp

@@ -0,0 +1,74 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+void move(int n, char src, char helper , char dest){
+
+	if (n ==0) return;
+
+
+	move(n-1,src,dest,helper);
+
+	cout<<"Shift disl"<<n << "from" <<src << "to" <<dest<<endl;
+
+	move(n-1,helper,src,dest);
+}
+
+
+
+
+int main() {
+    
+    
+    #ifndef ONLINE_JUDGE
+    // for getting input from input.txt
+    freopen("input.txt", "r", stdin);
+    // for writing output to output.txt
+    freopen("output.txt", "w", stdout);
+    #endif
+    
+    int n;
+
+    cin>>n;
+
+    move(n,'A','B','C');
+     
+     binary consist of only 0 and 1
+
+  pehle col vala loop h 
+  use sahi karo 
+  code m
+  mera code dekho idhar
+
+  map<char,int> a[100];
+
+  for(int i=0; i< str.len(); i++) { 
+  	a[str]++;
+
+  }
+   
+   for(ans: a) {
+
+   	  cout<<ans.key<<ans.value;
+   }
+
+
+
+    for(int i = 0;  i < col ; i ++) {
+    	for (int j = 0; j < row; j++) {
+    		if(mat[j][i] == 1) {
+    			ans = i;
+    			break;
+
+    		}
+    	}
+    }
+
+
+
+	retrun 0;
+}
+
+just iterate matrix and check whether it is 1 in column then it would return answer O(n2)
+
+

RatInMaze

@@ -0,0 +1,60 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+void generateBrackets(char *out, int n,
+	int idx, int open, int close){
+
+
+	if(idx == 2*n) {
+		out[idx] = '\0';
+
+		cout<< out <<endl;
+		return;
+	}
+ 
+
+ if (open < n) {
+
+ 	out[idx] = '{';
+ 	generateBrackets(out,n,idx+1,open+1,
+ 		close);
+ }
+
+ if (close < open) {
+
+ 	out[idx] = '}';
+ 	generateBrackets(out,n,idx+1,open,
+ 		close+1);
+ }
+  return;
+
+
+}
+
+
+
+
+int main() {
+
+    #ifndef ONLINE_JUDGE
+    // for getting input from input.txt
+    freopen("input.txt", "r", stdin);
+    // for writing output to output.txt
+    freopen("output.txt", "w", stdout);
+    #endif
+    
+    int n; 
+
+    cin>>n;
+    
+    char out[1000];
+
+    int idx = 0;
+
+    generateBrackets(out,n,idx,0,0);
+   
+
+
+	return 0; 
+}

RatInMaze.cpp

@@ -0,0 +1,63 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+void generateStrings(char *in,char *out,
+	int i, int j) {
+   
+   if(in[i] == '\0'){
+
+   	out[j] = '\0';
+
+   	cout << out <<endl;
+
+   	return;
+   }
+   
+   // rec case
+
+   int digit = in[i] - '0';
+   if (digit!= 0) {
+   char ch = digit + 'A' - 1;
+   out[j] = ch;
+
+   generateStrings(in,out,i+1,j+1);
+  }
+   if(in[i+1]!= '\0') {
+      
+      int secondDigit = in[i+1] - '0';
+
+      int no = digit*10 + secondDigit;
+      if(no <= 26) {
+      	char ch = no + 'A' - 1;
+      	out[j] = ch;
+      	generateStrings(in,out,i+2,j+1);
+      }
+
+   }
+
+   return;
+
+}
+
+int main () {
+
+   #ifndef ONLINE_JUDGE
+     // for getting input from input.txt
+    freopen("input.txt", "r", stdin);
+    // for writing output to output.txt
+    freopen("output.txt", "w", stdout);
+    #endif
+
+    char a[100];
+
+    cin>>a;
+
+    char out[100];
+
+    generateStrings(a,out,0,0);
+
+
+
+	return 0;
+}

StringPermutation.cpp

@@ -1 +1 @@
-1234
+123