leetcode Pascal's Triangle

Pascal's Triangle

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Question  Solution 

Total Accepted: 57134  Total Submissions: 188533  Difficulty: Easy

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]
]

这个只要发现规律就好，没行第一个为1，最后一个为1，中间的a[i][j]=a[i-1][j-1]+a[i-1][j]，所以只要填好一行后，然后压入结果就好。

class Solution {

public:
    vector<vector<int>> generate(int numRows) 
{
vector<int> temp;
vector<vector<int>> result;
if (numRows < 1)
return{};
temp.push_back(1);
int m = 0;
result.push_back(temp);
temp.clear();
for (int i = 2; i <= numRows; i++)
{
temp.push_back(1);
for (int j = 2; j < i; j++)
{
m = result[i - 2][j - 2] + result[i - 2][j-1];
temp.push_back(m);
}
temp.push_back(1);
result.push_back(temp);
temp.clear();
}
return result;
}
};