Pascal's Triangle II

class Solution {public:    vector<int> getRow(int rowIndex) {        vector<int> cur;if(rowIndex < 0) return cur;vector<int> pre;pre.push_back(1);if(rowIndex ==0) return pre;for(int i=1;i<=rowIndex;i++){cur.clear();for(int j=0;j<=i;j++){if(j==0 || j==i){cur.push_back(1);}else{cur.push_back(pre[j-1]+pre[j]);}}pre=cur;}return cur;    }};