Leetcode 118

The idea of this solution is pretty simple:

We first have a matrix array called res
Then we loop through numRows
While iterating through numRows we have to make an array called temp. It is going to be our current row.
We make temp[0] and temp[len(temp)] equal to 1 so we get the outer 1’s.
Then we loop through the middle elements (basically excluding the outside 1’s)
We have to make every temp[j] equal to the previous rows previous rows[j - 1] + previous rows[j]. We do j - 1 and j. If you don’t understand, why look at the image below:
Then we append temp to res
After iterating, we can return res.

The Code:

func generate(numRows int) [][]int {
    res := [][]int{}

    for i := 0; i < numRows; i++ {
        temp := make([]int, i+1)
        temp[0], temp[len(temp)-1] = 1, 1
        for j := 1; j < len(temp)-1; j++ {
            temp[j] = res[i-1][j-1] + res[i-1][j]
        }
        res = append(res, temp)
    }

    return res
}

We can Take Out Temp And Get:

func generate(numRows int) [][]int {
    res := [][]int{}

    for i := 0; i < numRows; i++ {
        res = append(res, make([]int, i+1))
        res[i][0], res[i][len(res[i])-1] = 1, 1
        for j := 1; j < len(res[i])-1; j++ {
            res[i][j] = res[i-1][j-1] + res[i-1][j]
        }
    }

    return res
}