Stack DataStructure added

Author: Mansiprajapatii

data_structure/Stack/Delete_middle_element.cpp

@@ -0,0 +1,56 @@
+#include<iostream>
+#include<stack>
+using namespace std;
+
+void solve(stack<int>&inputStack, int count, int size){
+
+   //base case
+   if(count==size/2){
+      inputStack.pop();
+      return;
+   }
+
+   int num = inputStack.top();   //store the top element 
+   inputStack.pop(); //pop that element
+
+   //recursive call 
+   solve(inputStack,count+1, size);  
+
+   inputStack.push(num); // push back the top elements which pop in the process 
+}
+
+
+void deleteMiddle(stack<int>&inputStack, int N){
+	
+  int count =0;
+  solve(inputStack,count,N);
+   
+}
+
+int main(){
+
+    stack<int> inputStack;
+
+    inputStack.push(5);
+     inputStack.push(9);
+      inputStack.push(12);
+       inputStack.push(8);
+        inputStack.push(4);
+
+    int N = inputStack.size();
+
+    //  for(int i=0; i<N; i++){
+    //     cout<<inputStack.top()<<" ";
+    //     inputStack.pop();
+    // }
+    // cout<<endl;
+
+    deleteMiddle(inputStack,N);
+
+    for(int i=0; i<N; i++){
+        cout<<inputStack.top()<<" ";
+        inputStack.pop();
+    }
+
+    return 0;
+}

data_structure/Stack/Mini_cost_to_make_string_valid.cpp

@@ -0,0 +1,58 @@
+#include<iostream>
+#include<stack>
+using namespace std;
+int findMinimumCost(string str) {
+  	
+    //odd condition
+    if(str.length()%2 == 1) {
+        return -1;
+    }
+    
+    stack<char> s;
+    for(int i=0; i<str.length(); i++) {
+        char ch = str[i];
+        
+        if(ch == '{') 
+            s.push(ch);
+		else
+        {
+            //ch is closed brace
+            if(!s.empty() && s.top() == '{') {
+                s.pop();
+            }
+            else
+            {
+                s.push(ch);
+            }
+        }
+    }
+    
+        //stack contains invalid expression
+        int a = 0, b = 0;
+        while(!s.empty()) {
+            if(s.top() == '{') {
+                b++;
+            }
+            else
+            {
+                a++;
+            }
+            s.pop();
+        }
+        
+		int ans = (a+1)/2 + (b+1)/2;
+        return ans;
+    
+    
+}
+
+
+int main(){
+
+
+string s = "{{}{}}";
+
+cout<<findMinimumCost(s)<<endl;
+
+    return 0;
+}

data_structure/Stack/Next_smaller_element.cpp

@@ -0,0 +1,37 @@
+#include <iostream>
+#include<stack>
+#include<vector>
+using namespace std;
+
+vector<int> nextSmallerElement(vector<int>& arr, int n){
+    stack<int>s;
+
+    s.push(-1);
+    vector<int>ans(n);
+
+    for(int i=n-1; i>=0; i--){
+        int cur = arr[i];
+
+        while(s.top() >= cur){
+            s.pop();
+        }
+        //ans is stack ka top 
+        ans[i]=s.top();
+        s.push(cur);
+    }
+    return ans;
+}
+
+int main(){
+
+    int n= 4;
+    vector<int> arr= {2,1,4,3};
+    
+    vector<int>ans =nextSmallerElement(arr,n);
+
+    for(int i=0; i<n; i++){
+        cout<<ans[i]<<" ";
+    }
+
+    return 0;
+}

data_structure/Stack/Redundant_brackets.cpp

@@ -0,0 +1,51 @@
+#include<iostream>
+#include<stack>
+using namespace std;
+
+bool findRedundantBrackets(string &s)
+{
+    stack<char>st;
+
+    for(int i=0; i<s.length(); i++){
+        char ch = s[i];
+
+        if(ch=='(' || ch=='+' || ch=='-' || ch=='*' || ch=='/'){
+            st.push(ch);
+        }
+
+        else{
+
+            if(ch==')'){
+                bool isRedundant = true;
+
+                while(st.top()!='('){
+                    char top = st.top();
+
+                    if(top=='+' || top=='-' || top=='*' || top=='/'){
+                        isRedundant=false;
+                        st.pop();
+                    }
+                }
+
+                if(isRedundant == true){
+                    return true;
+                }
+
+                  st.pop();
+            }
+        }
+    }
+
+    return false;
+
+
+}
+
+int main(){
+
+ string s = "(a+c*b)+(c))";
+
+ cout<<findRedundantBrackets(s)<<endl;
+
+return 0;
+}

data_structure/Stack/Reverse_stack_using_recursion.cpp

@@ -0,0 +1,61 @@
+#include<iostream>
+#include<stack>
+using namespace std;
+
+
+
+void insertAtBottom(stack<int> &stack, int x){
+    if(stack.empty()){
+        stack.push(x);
+        return;
+    }
+
+    int num = stack.top();
+    stack.pop();
+
+    insertAtBottom(stack, x);
+
+    stack.push(num);
+}
+
+void reverseStack(stack<int> &stack) {
+    
+    //base case
+    if(stack.empty()){
+        return;
+    }
+
+    int num = stack.top();
+    stack.pop();
+
+    reverseStack(stack);
+
+    insertAtBottom(stack,num);
+}
+
+int main(){
+
+    stack<int> inputStack;
+
+    inputStack.push(5);
+     inputStack.push(9);
+      inputStack.push(12);
+       inputStack.push(8);
+        inputStack.push(4);
+
+//          for(int i=0; i<5; i++){
+//     cout<<inputStack.top()<<" ";
+//     inputStack.pop();
+//  }
+
+ reverseStack(inputStack);
+
+ for(int i=0; i<5; i++){
+    cout<<inputStack.top()<<" ";
+    inputStack.pop();
+ }
+
+
+return 0;
+
+}

data_structure/Stack/Reverse_string_using_stack.cpp

@@ -0,0 +1,30 @@
+#include<iostream>
+#include<stack>
+
+using namespace std;
+
+int main(){
+
+    string str = "life";
+
+    cout<<str<<endl;
+
+    stack <char> s;
+
+    for(int i=0; i<str.length(); i++){
+        char ch = str[i];
+        s.push(ch);
+    }
+
+    string ans ="";
+
+    while(!s.empty()){
+        char c = s.top();
+        ans.push_back(c);
+        s.pop();
+    }
+
+    cout<<ans<<endl;
+
+    return 0;
+}

data_structure/Stack/Sort_stack.cpp

@@ -0,0 +1,59 @@
+#include<iostream>
+#include<stack>
+using namespace std;
+
+void sort(stack<int> &stack, int x){
+
+	//base case
+	if(stack.empty() || !stack.empty() && stack.top() < x ){
+		stack.push(x);
+		return;
+	}
+
+	int n = stack.top();
+	stack.pop();
+
+	sort(stack,x);
+
+	stack.push(n);
+
+}
+
+void sortStack(stack<int> &stack)
+{
+	//base case
+	if(stack.empty()){
+		return;
+	}
+
+	int num = stack.top();
+	stack.pop();
+    
+	sortStack(stack);
+
+	sort(stack,num);
+
+}
+
+
+int main(){
+
+    stack<int> inputStack;
+
+    inputStack.push(5);
+     inputStack.push(9);
+      inputStack.push(12);
+       inputStack.push(8);
+        inputStack.push(4);
+
+        sortStack(inputStack);
+
+         for(int i=0; i<5; i++){
+    cout<<inputStack.top()<<" ";
+    inputStack.pop();
+ }
+
+
+        return 0;
+
+}