leetcode119

public class Solution {
    public IList<int> GetRow(int rowIndex) {
        List<List<int>> list = new List<List<int>>();
            for (int i = 0; i <= rowIndex; i++)
            {
                var row = new List<int>();
                if (i == 0)
                {
                    row.Add(1);
                }
                else if (i == 1)
                {
                    row.Add(1);
                    row.Add(1);
                }
                else//i>=3
                {
                    for (int j = 0; j <= i; j++)
                    {
                        if (j == 0)
                        {
                            row.Add(1);
                        }
                        else if (j == i)
                        {
                            row.Add(1);
                        }
                        else
                        {
                            var pre = list[i - 1];
                            row.Add(pre[j - 1] + pre[j]);
                        }
                    }
                }
                list.Add(row);
            }
            var result = list.LastOrDefault();
            return result;
    }
}

https://leetcode.com/problems/pascals-triangle-ii/#/description

 

Python的实现：

class Solution:
    def getRow(self, rowIndex: int) -> List[int]:
        if rowIndex == 0:
            return [1]
        elif rowIndex == 1:
            return [1,1];
        else:
            tri = []
            tri.append([1])            
            for i in range(1,rowIndex+1):
                pre = [0] + tri[i-1] + [0]
                newrow = []
                for j in range(len(pre)-1):
                    newrow.append(pre[j]+pre[j+1])
                tri.append(newrow)
            return tri[rowIndex]

 

Java版：

class Solution {
    public List<Integer> getRow(int rowIndex) {        
        if(rowIndex == 0){
            List<Integer> l = new ArrayList<Integer>();
            l.add(1);
            return l;        
        }else{
            List<List<Integer>> list = new ArrayList<List<Integer>>();
            List<Integer> l1 = new ArrayList<Integer>();
            l1.add(1);
            list.add(l1);
            for(int i=1;i<=rowIndex;i++){
                List<Integer> pre = list.get(i-1);
                List<Integer> newrow = new ArrayList<Integer>();
                newrow.add(1);

                for(int j=0;j<pre.size()-1;j++){
                    int cur = pre.get(j) + pre.get(j+1);
                    newrow.add(cur);
                }

                newrow.add(1);
                list.add(newrow);
            }
            return list.get(rowIndex);
        }
    }
}