leetcode 130: Pascal's Triangle II

Pascal's Triangle II Oct 29 '12 461 / 1118

Given an index k, return the k^th row of the Pascal's triangle.

For example, given k = 3,
Return [1,3,3,1].

Note:
Could you optimize your algorithm to use only O(k) extra space?

public class Solution {
    public List<Integer> getRow(int rowIndex) {
        List<Integer> res = new ArrayList<Integer>(rowIndex);
        
        if(rowIndex<0) return res;
        
        for(int i=0; i<=rowIndex; i++) {
            res.add(1);
            for(int j=i-1;j>0; j--) {
                res.set(j, res.get(j-1)+res.get(j));
            }
        }
        return res;
    }
}

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        //kth k+1 length [1,3,3,1]
        
        //assert(rowIndex>0);
        vector<int>* pre = new vector<int>(rowIndex+1);
        vector<int>* cur = new vector<int>(rowIndex+1);
        
        for(int i=0; i<=rowIndex; i++) {
            for(int j=0; j<=i; j++) {
                if(j==0 || j==i) (*cur)[j] = 1;
                else {
                    (*cur)[j] = (*pre)[j-1] + (*pre)[j];
                }
            } 
            swap(pre,cur);
        }
        delete cur;
        return *pre;
    }
};