Create binary-search.cpp

arrays/reverse-array/reversearray.cpp

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+
+// REVERSE AN ARRAY
+
+#include<iostream>
+using namespace std;
+
+void reArr(int arr[],int start ,int last){  // function to reverse array
+
+  int temp;
+
+  while(start <last){
+    temp =arr[start];        // simple swap
+    arr[start]=arr[last];
+    arr[last]=temp;
+    last--;
+    start++;
+  }
+}
+
+
+int main(){
+ int n;
+ cout<<"Enter size of array : ";
+ cin>>n;
+ int arr[n];
+ cout<<"Enter the element of array\n";
+
+  for(int i=0;i<n;i++){
+    cin>>arr[i];
+  }
+ reArr(arr,0,n-1);            //  function for reverse array element
+ cout<<"Reversed array\n";
+
+ for(int i=0;i<n;i++){
+    cout<<arr[i]<<" ";
+ }
+
+ return 0;
+}

arrays/searching/binary-search/binary-search.cpp

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+
+//Binary search .................Iterative method best for sorted array
+
+# include<bits/stdc++.h>
+using namespace std; //std::cout or std::cin
+
+int main(){
+  int n,t;
+  cout<<"enter test cases"<<endl;
+  cin>>t;
+                               //cout<<(sizeof(arr)/sizeof(arr[0]));   sizeof(arr) = datatype of arr * number of variable
+  while(t--){
+        cout<<"enter size of array "<<endl;
+           cin>>n;
+    int arr[n];
+
+    cout<<"Enter array element\n";
+
+  for(int i=0;i<n;i++){
+    cin>>arr[i];
+    }
+
+    int key;
+    cout<<"enter key to search"<<endl;
+    cin>>key;
+
+    int low=0,high=n-1, flag=0;
+    for(int i=0;i<n;i++){
+                                                                // int mid =(low +high)/2; //It take more time 5.2 second
+                                                               // cout<<mid;
+       int mid=low+(high-low)/2;                      //     rather using (low+high)/2  we use this bez   It take less time 4.1 second
+       if(arr[mid]==key){
+        cout<<"present"<<endl;
+          flag=1;
+          break;
+       }
+       else if(arr[mid]>key){            
+             high= mid-1;
+       }
+       else if(arr[mid] <key)
+          low = mid+1;
+    }
+
+    if(flag==0){                             
+        cout<<"Not present"<<endl;
+    }
+  }
+  return 0;
+}

arrays/searching/linear-search/linear-search.cpp

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+//Linear search key
+
+#include<bits/stdc++.h>
+using namespace std;
+
+int main(){
+ int n;                                // size of array
+ cout<<"enter size of array"<<endl;
+ cin>>n;
+ int arr[n]; // array to store all the elements
+
+ cout<<"Enter array element\n";
+ for(int i=0 ;i<n;i++){
+     cin>>arr[i]; // loop for entering array
+ }
+ int key; // key variable to be search
+ cout<<"enter key to be search"<<endl;
+ cin>>key;
+ int i =0 ,flag =0 ,count =0,lastpos;
+ for(i =0 ; i<n ;i++) {
+        if(key == arr[i]){
+           // cout<<"present"<<" "<<i+1<<endl;
+           lastpos=i+1;
+            flag =1;
+            break;
+           // break; using this break statment present will run only 1 time if same element array then it will stop at first time
+           // using break time compx O(1)
+           // without break we can print both 1 or all position of key present in array
+        }
+        count++;
+ }
+ if(flag == 0){
+    cout<<"Not present"<<endl;
+ } else {
+ cout<<"present \n position"<<lastpos<<endl;                      // time compx  O(n)
+  //cout<<count<<endl;
+ }
+
+return 0;
+}