added important code

Array/best_time_to_buy_and_sell_stock.c++

@@ -1,29 +1,35 @@
 #include <bits/stdc++.h>
 using namespace std;
 
-int maxProfit(vector<int>& prices) {
- int max_so_far=0;
- int max_ending_here=0;
- for(int i=1;i<prices.size();i++){
- max_ending_here+=prices[i]-prices[i-1];
- if(max_ending_here>max_so_far){
- max_so_far=max_ending_here;
+int maxProfit(vector<int> &prices)
+{
+ int max_so_far = 0;
+ int max_ending_here = 0;
+ for (int i = 1; i < prices.size(); i++)
+ {
+ max_ending_here += prices[i] - prices[i - 1];
+ if (max_ending_here > max_so_far)
+ {
+ max_so_far = max_ending_here;
  }
- if(max_ending_here<0){
- max_ending_here=0;
+ if (max_ending_here < 0)
+ {
+ max_ending_here = 0;
  }
  }
  return max_so_far;
 }
 
-int main(){
+int main()
+{
  int n;
- cin>>n;
- vector <int> v;
- for(int i=0;i<n;i++){
+ cin >> n;
+ vector<int> v;
+ for (int i = 0; i < n; i++)
+ {
  int x;
- cin>>x;
+ cin >> x;
  v.push_back(x);
  }
- cout<<maxProfit(v)<<endl;
+ cout << maxProfit(v) << endl;
 }

Array/find_duplicate_in_array.c++

@@ -0,0 +1,20 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int findDup(vector<int> &arr)
+{
+ int slow = arr[0];
+ int fast = arr[0];
+ do
+ {
+ slow = arr[slow];
+ fast = arr[arr[fast]];
+ } while (slow != fast);
+ fast = arr[0];
+ while (slow != fast)
+ {
+ slow = arr[slow];
+ fast = arr[fast];
+ }
+ return slow;
+}

Array/four_sum.cpp

@@ -0,0 +1,43 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+vector<vector<int>> fourSum(vector<int> &nums, int target)
+{
+ vector<vector<int>> ans;
+ if (nums.empty())
+ return ans;
+ int n = nums.size();
+ sort(nums.begin(), nums.end());
+ for (int i = 0; i < n; i++)
+ {
+ for (int j = i + 1; j < n; j++)
+ {
+ int tar2 = target - nums[i] - nums[j];
+ int front = j + 1;
+ int back = n - 1;
+ while (front < back)
+ {
+ int twosum = nums[front] + nums[back];
+ if (twosum < tar2)
+ front++;
+ else if (twosum > tar2)
+ back--;
+ else
+ {
+ vector<int> quad;
+ quad = {nums[i], nums[j], nums[front], nums[back]};
+ ans.push_back(quad);
+ while (front < back && nums[front] == quad[2])
+ ++front;
+ while (front < back && nums[back] == quad[3])
+ --back;
+ }
+ }
+ while (j + 1 < n && nums[j] == nums[j + 1])
+ ++j;
+ }
+ while (i + 1 < n && nums[i] == nums[i + 1])
+ ++i;
+ }
+ return ans;
+}

Array/kadane_algorithm.c++

@@ -1,28 +1,34 @@
 #include <bits/stdc++.h>
 using namespace std;
 
-int solve(int arr[],int n){
- int max_so_far=INT_MIN;
+int solve(int arr[], int n)
+{
+ int max_so_far = INT_MIN;
  int max_ending_here = 0;
- for(int i=0;i<n;i++){
- max_ending_here+=arr[i];
- if(max_ending_here>max_so_far){
- max_so_far=max_ending_here;
+ for (int i = 0; i < n; i++)
+ {
+ max_ending_here += arr[i];
+ if (max_ending_here > max_so_far)
+ {
+ max_so_far = max_ending_here;
  }
- if(max_ending_here<0){
- max_ending_here=0;
+ if (max_ending_here < 0)
+ {
+ max_ending_here = 0;
  }
  }
  return max_so_far;
 }
 
-int main(){ 
+int main()
+{
  int n;
- cin>>n;
+ cin >> n;
  int arr[n];
- for(int i=0;i<n;i++){
- cin>>arr[i];
+ for (int i = 0; i < n; i++)
+ {
+ cin >> arr[i];
  }
- cout<<solve(arr,n);
- cout<<endl;
+ cout << solve(arr, n);
+ cout << endl;
 }

Array/kth_min_element.cpp

@@ -1,23 +1,25 @@
-#include<bits/stdc++.h>
+#include <bits/stdc++.h>
 using namespace std;
 
-int kThMin(int arr[],int n,int k){
- sort(arr,arr+n);
- return arr[k-1];
+int kThMin(int arr[], int n, int k)
+{
+ sort(arr, arr + n);
+ return arr[k - 1];
 }
 
 int main()
- {
- //code
+{
+ //code
 
  int n;
- cin>>n;
+ cin >> n;
  int arr[n];
- for(int i=0;i<n;i++){
- cin>>arr[i];
+ for (int i = 0; i < n; i++)
+ {
+ cin >> arr[i];
  }
  int k;
- cin>>k;
- cout<<kThMin(arr,n,k)<<endl;
- return 0;
+ cin >> k;
+ cout << kThMin(arr, n, k) << endl;
+ return 0;
 }

Array/maximum_product_subarray.cpp

@@ -18,7 +18,7 @@ ll maxProduct(int arr[], int n)
  {
  max_ending_here = abs(max_ending_here);
  }
- cout<<max_ending_here<<" ";
+ cout << max_ending_here << " ";
  }
  return max_so_far;
 }

Array/merge_overlapping_intervals.cpp

@@ -0,0 +1,28 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+vector<vector<int>> merge(vector<vector<int>> &intervals)
+{
+ vector<vector<int>> ans;
+ if (intervals.size() == 0)
+ return ans;
+ else
+ {
+ sort(intervals.begin(), intervals.end());
+ vector<int> curr = intervals[0];
+ for (auto j : intervals)
+ {
+ if (j[0] <= curr[1])
+ {
+ curr[1] = max(curr[1], j[1]);
+ }
+ else
+ {
+ ans.push_back(curr);
+ curr = j;
+ }
+ }
+ ans.push_back(curr);
+ return ans;
+ }
+}

Array/negative_elements_to_one_side.c++

@@ -1,37 +1,47 @@
 #include <bits/stdc++.h>
 using namespace std;
 
-void solve(int arr[],int n){
+void solve(int arr[], int n)
+{
  int start = 0;
- int end = n-1;
- while(start<=end){
- if(arr[start]<0&&arr[end]<0){
+ int end = n - 1;
+ while (start <= end)
+ {
+ if (arr[start] < 0 && arr[end] < 0)
+ {
  start++;
  }
- else if(arr[start]>0&&arr[end]>0){
+ else if (arr[start] > 0 && arr[end] > 0)
+ {
  end--;
- } else if(arr[start]>0&&arr[end]<0){
- swap(arr[start],arr[end]);
+ }
+ else if (arr[start] > 0 && arr[end] < 0)
+ {
+ swap(arr[start], arr[end]);
  start++;
  end--;
  }
- else{
+ else
+ {
  start++;
  end--;
  }
  }
 }
 
-int main(){
+int main()
+{
  int n;
- cin>>n;
+ cin >> n;
  int arr[n];
- for(int i=0;i<n;i++){
- cin>>arr[i];
+ for (int i = 0; i < n; i++)
+ {
+ cin >> arr[i];
  }
- solve(arr,n);
- for(int i=0;i<n;i++){
- cout<<arr[i]<<" ";
+ solve(arr, n);
+ for (int i = 0; i < n; i++)
+ {
+ cout << arr[i] << " ";
  }
- cout<<endl;
+ cout << endl;
 }

Array/reverse_an_array.cpp

@@ -1,26 +1,31 @@
 #include <bits/stdc++.h>
 using namespace std;
 
-void solve(int arr[],int start,int end){
- while(start<end){
+void solve(int arr[], int start, int end)
+{
+ while (start < end)
+ {
  int temp = arr[start];
- arr[start]= arr[end];
- arr[end]=temp;
+ arr[start] = arr[end];
+ arr[end] = temp;
  start++;
  end--;
  }
 }
 
-int main(){
+int main()
+{
  int n;
- cin>>n;
+ cin >> n;
  int arr[n];
- for(int i=0;i<n;i++){
- cin>>arr[i];
+ for (int i = 0; i < n; i++)
+ {
+ cin >> arr[i];
  }
- solve(arr,0,n-1);
- for(int i=0;i<n;i++){
- cout<<arr[i]<<" ";
+ solve(arr, 0, n - 1);
+ for (int i = 0; i < n; i++)
+ {
+ cout << arr[i] << " ";
  }
- cout<<endl;
+ cout << endl;
 }