# Day2: (Arrays)

1. [**Set Matrix Zeros** ](https://leetcode.com/problems/set-matrix-zeroes/)\
   Looked for answer on 16th July 2020

```python
def setZeroes(self, matrix: List[List[int]]) -> None:
    """
    Do not return anything, modify matrix in-place instead.
    """
    rows = []
    columna = []
    for i in range(0 , len(matrix)):
        for j in range(0 , len(matrix[i])):
            if matrix[i][j] == 0:
                if i not in rows:
                    rows.append(i)
                if j not in columna:
                    columna.append(j)
    print (rows, columna)
    for i in rows:
        for j in range(0 , len(matrix[i])):
            matrix[i][j] = 0
    for i in columna:
        for j in range(0 , len(matrix)):
            matrix[j][i] = 0
```

[**2. Pascals Triangle**](https://leetcode.com/problems/pascals-triangle/)\
Solved on: 17th July 2020

```python
def generate(self, numRows: int) -> List[List[int]]:
    l=[]
    for i in range(numRows):
        k=[]
        for j in range(i+1):
            if j==0 or j==i:
                k.append(1)
            else:
                k.append(l[i-1][j-1] + l[i-1][j])
        l.append(k)
    return (l)

```

[**3. Next Permutation**](https://leetcode.com/problems/next-permutation/submissions/)\
Learnt on 17th July 2020

{% tabs %}
{% tab title="Python" %}

```python
def nextPermutation(self, arr: List[int]) -> None:
    """
    Do not return anything, modify nums in-place instead.
    """
    inverse_point = len(arr)-2
    
    while (inverse_point >=0 and arr[inverse_point] >= arr[inverse_point+1]):
        inverse_point = inverse_point-1
    
    if (inverse_point < 0):
        return []
    
    for i in reversed(range(inverse_point, len(arr))):
        if (arr[i] > arr[inverse_point]):
            arr[i], arr[inverse_point] = arr[inverse_point], arr[i]
    
    arr[inverse_point+1:] = reversed(arr[inverse_point+1:])
        
```

{% endtab %}

{% tab title="C++" %}

```
public:
    void nextPermutation(vector<int>& nums) {
        next_permutation(nums.begin(), nums.end());
    }
```

{% endtab %}
{% endtabs %}

[Stock Buy and Sell ](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/submissions/)\
Learnt on 24th July 2020

{% tabs %}
{% tab title="Python" %}

```python
class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        if (len(prices) ==0):
            return 0
        min_price=prices[0]
        max_profit=0
        for item in prices:
            profit = item - min_price
            if profit > max_profit:
                max_profit = profit
            if item <= min_price:
                min_price = item
        return max_profit
```

{% endtab %}

{% tab title="CPP" %}

```cpp
int maxProfit(vector<int>& prices) {
    int n=prices.size();
    if (n==0) {
        return 0;
    }
    int profit=0, max_profit=0, min_price=prices[0];
    for (int i=0;i<n;i++) {
        profit = prices[i]-min_price;
        if (profit > max_profit) {
            max_profit = profit;
        }
        if (prices[i] < min_price) {
            min_price= prices[i];
        }
    }
    return max_profit;
}
```

{% endtab %}
{% endtabs %}

[ 6. Rotate Matrix 90 degree](https://leetcode.com/problems/rotate-image/)\
Learnt on  27th July 2020

```cpp
void rotate(vector<vector<int>>& matrix) {
    // Transpose matrix
     for (int i=0; i<size(matrix);i++) {
         for (int j=i; j<size(matrix); j++) {
             int temp = matrix[i][j];
             matrix[i][j] = matrix[j][i];
             matrix[j][i] = temp;
         }
     }
        
    int n =size(matrix);
    //  Reverse row elements
    for (int i=0;i<n;i++){
        for (int j=0;j<n/2;j++) {
                int temp = matrix[i][j];
                matrix[i][j] = matrix[i][n-j-1];;
                matrix[i][n-j-1] = temp;
        }
    }
}
```


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