118. 杨辉三角

class Solution:
    def generate(self, numRows: int) -> List[List[int]]:
        res = []
        for i in range(numRows):
            t = [1 if j == 0 or j == i else 0 for j in range(i + 1)]
            for j in range(1, i):
                t[j] = res[i - 1][j - 1] + res[i - 1][j]
            res.append(t)
        return res

class Solution {
    public List<List<Integer>> generate(int numRows) {
        List<List<Integer>> res = new ArrayList<>();
        for (int i = 0; i < numRows; ++i) {
            List<Integer> t = new ArrayList<>();
            for (int j = 0; j < i + 1; ++j) {
                boolean firstOrLast = j == 0 || j == i;
                t.add(firstOrLast ? 1 : 0);
            }
            for (int j = 1; j < i; ++j) {
                int val = res.get(i - 1).get(j - 1) + res.get(i - 1).get(j);
                t.set(j, val);
            }
            res.add(t);
        }
        return res;
    }
}

function generate(numRows: number): number[][] {
    if (numRows == 0) return [];
    let ans = [[1]];
    for (let i = 1; i < numRows; ++i) {
        ans.push(new Array(i + 1).fill(1));
        let half = i >> 1;
        for (let j = 1; j <= half; ++j) {
            let cur = ans[i - 1][j - 1] + ans[i - 1][j];
            ans[i][j] = cur;
            ans[i][i - j] = cur;
        }
    }
    return ans;
}

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> res;
        for (int i = 0; i < numRows; ++i) {
            vector<int> t(i + 1);
            t[0] = 1;
            t[i] = 1;
            for (int j = 1; j < i; ++j) {
                t[j] = res[i - 1][j - 1] + res[i - 1][j];
            }
            res.push_back(t);
        }
        return res;
    }
};

func generate(numRows int) [][]int {
	res := make([][]int, numRows)
	for i := 0; i < numRows; i++ {
		t := make([]int, i+1)
		t[0] = 1
		t[i] = 1
		for j := 1; j < i; j++ {
			t[j] = res[i-1][j-1] + res[i-1][j]
		}
		res[i] = t
	}
	return res
}

const generate = function (numRows) {
    let arr = [];
    for (let i = 0; i < numRows; i++) {
        let row = [];
        row[0] = 1;
        row[i] = 1;
        for (let j = 1; j < row.length - 1; j++) {
            row[j] = arr[i - 1][j - 1] + arr[i - 1][j];
        }
        arr.push(row);
    }
    return arr;
};