119. 杨辉三角 II

原题

https://leetcode.cn/problems/pascals-triangle-ii/description/

思路

动态规划

复杂度

时间：O(n²)
空间：O(n²)

Python代码

class Solution:
    def getRow(self, rowIndex: int) -> List[int]:
        triangles = []
        for i in range(rowIndex + 1):
            # 当前行
            row = []
            if i == 0:
                row.append(1)
            else:
                # 上一行
                prev = triangles[i - 1]
                row.append(1)
                for j in range(i - 1):
                    row.append(prev[j] + prev[j + 1])
                row.append(1)
            triangles.append(row)
        return triangles[rowIndex]

Go代码

func getRow(rowIndex int) []int {
	var triangles [][]int
	for i := 0; i <= rowIndex; i++ {
		// 当前行
		row := []int{}
		if i == 0 {
			row = append(row, 1)
		} else {
			// 上一行
			prev := triangles[i-1]
			row = append(row, 1)
			for j := 0; j < i-1; j++ {
				row = append(row, prev[j]+prev[j+1])
			}
			row = append(row, 1)
		}
		triangles = append(triangles, row)
	}
	return triangles[rowIndex]
}