"Leetcode-Interview algorithm classic-java Implementation" "119-pascal ' s Triangle II (Pascal triangle (Yang Hui triangle) II)"

Source: Internet
Author: User

"119-pascal ' s Triangle II (Pascal triangle (Yang Hui triangle) II)" "leetcode-Interview algorithm classic-java Implementation" "All topics Directory Index" Original Question

Given an index k, return the kth row of the Pascal ' s triangle.
For example, given k = 3,
Return [1,3,3,1] .
Could optimize your algorithm to use only O (k) extra space?

Main Topic

Given a positive integer k, the K-line of Pascal is obtained.

Thinking of solving problems

For any n>0, there are
F (1, N) =1, (n>0)
F (n, N) =1, (N>2)
F (i,j) = f (i-1, j-1) +f (i, j-1), I>2,j>2,
Ask for the K line.

Code Implementation

Algorithm implementation class

Import java.util.*; Public classSolution { PublicList<integer>GetRow(intRowIndex) {rowindex++;//rowindex number of substantive data        if(RowIndex <0) {return NULL; } list<integer> result =NewArraylist<> (RowIndex);if(RowIndex >=1) {Result.add (1); }if(RowIndex >=2) {Result.add (1); }intline =0;//record which line is currently in use        intPrev//What line is on the previous line        if(RowIndex >=3) {int[] data =New int[2][rowindex];//"1"data[0][0] =1; data[1][0] =1; data[1][1] =1; for(inti =2; i < RowIndex; i++) {line = i%2;//New calculated data is saved on line No. 0 or 1thPrev = (I-1+2) %2;//data[line][0] = 1;//Set the first number, no, "1" is already in place, Data[x][0] Total is 1                 for(intj =1; J < I; J + +) {Data[line][j] = data[prev][j-1] + data[prev][j]; } Data[line][i] =1;//Set last number}// Result.clear (); for(inti =0; i < RowIndex;            i++) {Result.add (data[line][i]); }        }returnResult }}
Evaluation Results

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"Leetcode-Interview algorithm classic-java Implementation" "119-pascal ' s Triangle II (Pascal triangle (Yang Hui triangle) II)"

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