Add arrays folder

Array/alternatePosneg.cpp

@@ -0,0 +1,88 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+void solve()
+{
+    cout << "Inside solve" << endl;
+    vector<int> v{-5, -2, 5, 2, 4, 7, -8,13,14,-15,-17,-19,-10,-57,-56};
+    int n = v.size();
+
+    /*----------------O(n^2) approach-------------*/
+
+    // for (int i = 1; i < n; i++)
+    // {
+    //     if (v[i] * v[i - 1] < 0)
+    //         continue;
+    //     else
+    //     {
+    //         int j;
+    //         for (j = i + 1; j < n; j++)
+    //         {
+    //             if (v[i] * v[j] < 0)
+    //             {
+    //                 swap(v[i], v[j]);
+    //                 break;
+    //             }
+    //         }
+    //         if (j == n)
+    //             break;
+    //     }
+    // }
+
+    /*-------------------------------------------*/
+
+
+    /*----------------O(nlogn) approach-------------*/
+
+    // sort(v.begin(), v.end());
+
+    /*-------------------------------------------*/
+
+    /*----------------O(n) approach-------------*/
+    int left=0,right=n-1;
+    while(left < right){
+        while(left < n && v[left] < 0)
+            left++;
+        while(right >= 0 && v[right] >= 0)
+            right--;
+        if(left<right)
+            swap(v[left],v[right]);
+    }
+    /*-------------------------------------------*/
+    int negEnd, pos = 0, neg = 0;
+
+    for (int i = 0; i < n; i++)
+    {
+        if (v[i] < 0)
+            continue;
+        else
+        {
+            negEnd = i - 1;
+            break;
+        }
+    }
+    for (auto x : v)
+        cout << x << " ";
+    cout<<endl;
+    int posStart = negEnd + 1, posEnd = n - 1;
+    int i;
+    for (i = 1; i < n && posStart < n; i++)
+    {   
+        if(v[i] * v[i-1] <= 0)
+            continue;
+        else{
+            swap(v[i],v[posStart]);
+            posStart++;
+        }
+    }
+
+
+    for (auto x : v)
+        cout << x << " ";
+    cout<<endl;
+}
+
+int main(){
+    solve();
+    return 0;
+}