标签：style blog color 使用 io strong for div
Given an index k, return the kth row of the Pascal‘s triangle.
For example, given k = 3,
Return [1,3,3,1].
Note:
Could you optimize your algorithm to use only O(k) extra space?
思路：对于Pascal三角形的每一行，其两端元素为1，而中间元素curr[i]=prev[i-1]+prev[i]。为了求得第k行，使用依次迭代求解即可。同时，利用每一行的对称性优化内循环。
1 class Solution { 2 public: 3 vector<int> getRow( int rowIndex ) { 4 if( rowIndex < 0 ) { return vector<int>( 0 ); } 5 vector<int> pascal( 1, 1 ); 6 for( int i = 1; i <= rowIndex; ++i ) { 7 vector<int> tmp_pascal( i+1, 1 ); 8 for( int k = 1; k <= i/2; ++k ) { 9 tmp_pascal[k] = tmp_pascal[i-k] = pascal[k-1] + pascal[k]; 10 } 11 pascal = tmp_pascal; 12 } 13 return pascal; 14 } 15 };
Pascal's Triangle II,布布扣,bubuko.com
标签：style blog color 使用 io strong for div
原文地址：http://www.cnblogs.com/moderate-fish/p/3913567.html
