Leetcode 119.Pascal's Triangle II
2017-12-29 15:58
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这道题是118题的延续,要求给定数字k,返回杨辉三角的第k行,这里把最开始的[1]这一行看作了第0行。
方法1:在118题上直接改了下.
class Solution {
public:
vector<int> getRow(int rowIndex) {
vector<vector<int>>re;
for(int i=0; i<=rowIndex; ++i)
{
re.push_back(vector<int>(i+1,1));
for(int j=1; j<i; ++j)
re[i][j]=re[i-1][j-1]+re[i-1][j];
}
return re.back();
}
};
方法2:这题目只要求求一行,就不建二维数组了,直接在一维数组里面一行行求出来。
方法1:在118题上直接改了下.
class Solution {
public:
vector<int> getRow(int rowIndex) {
vector<vector<int>>re;
for(int i=0; i<=rowIndex; ++i)
{
re.push_back(vector<int>(i+1,1));
for(int j=1; j<i; ++j)
re[i][j]=re[i-1][j-1]+re[i-1][j];
}
return re.back();
}
};
方法2:这题目只要求求一行,就不建二维数组了,直接在一维数组里面一行行求出来。
class Solution { public: vector<int> getRow(int rowIndex) { vector<int>re(rowIndex+1,0); re[0]=1; for(int i=1; i<=rowIndex; ++i) { for(int j=i; j>=1; --j) re[j]+=re[j-1]; } return re; } };
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