leetcode—pascal triangle

1.题目描述

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] ]

 

2.解法分析

这个题目很简单,所以不需要额外的解说,一遍就AC了

class Solution { public: vector<vector<int> > generate(int numRows) { // Start typing your C/C++ solution below // DO NOT write int main() function //by [e-mail] vector<vector<int> > pascal; if(numRows <= 0)return pascal; vector<int> firstRow ; firstRow.push_back(1); pascal.push_back(firstRow); if(numRows == 1)return pascal; firstRow.push_back(1); pascal.push_back(firstRow); if(numRows == 2)return pascal; for(int i = 2;i<numRows;++i) { vector<int> curRow; curRow.assign(i+1,0); curRow[0]= 1; curRow[i] =1; for(int j =1;j<i;++j) { curRow[j]=pascal[i-1][j-1]+pascal[i-1][j]; } pascal.push_back(curRow); } return pascal; } };