【Pascal's Triangle】cpp

题目：

Given numRows, generate the first numRows of Pascal‘s triangle.

For example, given numRows = 5,
Return

[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

代码：

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
            vector<vector<int> > ret;
            if ( numRows<1 ) return ret;
            vector<int> pre, curr;
            for ( int i=0; i<numRows; ++i )
            {
                curr.clear();
                curr.push_back(1);
                for ( int j=0; j<pre.size(); ++j )
                {
                    if ( j==pre.size()-1 ){
                        curr.push_back(1);
                    }
                    else{
                        curr.push_back(pre[j]+pre[j+1]);
                    }
                }
                pre = curr;
                ret.push_back(curr);
            }
            return ret;
    }
};

tips：

数组基本操作。

【Pascal's Triangle】cpp