https://oj.leetcode.com/problems/pascals-triangle-ii/

类似DP的迭代方法，只需注意数组大小分配即可。

class Solution {public:    int n,m;    vector
     
       c[2];    vector
      
        getRow(int rowIndex) {        n=rowIndex;        c[0].resize(n+1,0);        c[1].resize(n+1,0);        c[0][0]=1;        for (int i=1;i<=n;i++){            int cur=i%2;            int prev=(i-1)%2;            c[cur][0]=1;            c[cur][i]=1;            for (int j=1;j