README.md

Things I learned in: Day_19

Note: use the github provided TOC for navigaing.

Two pointer:

main concept of two pointer is if current sum is not equal to

int main(){
    int arr[1000] = {1,2,3};       // array should be sorted
    int n = 3;
    int key;
    cin>>key;

    for (int i = 0; i < n; ++i){
        /* code */
        cin>>arr[i];
    }

    int i = 0;
    int j = sizeof(arr)/sizeof(int);
    while(i<j){
        int current_sum = arr[i] + arr[j];
        if(current_sum>key){
            j--;
        } 
        else if(current_sum<key){
            i++;
        }
        else{
            cout<<arr[i]<<" "<<arr[j];
            i++;
            j--;
        }
    }
}

Binary search:

```cpp int binary_search(int a[],int n,int key){ int s=0; int e = n-1; while(s<=e){ int mid = (s+e)/2; if(a[mid]==key){ return mid; } else if(a[mid]>key){ e = mid-1; } else{ s = mid + 1; } } return -1; } ```