Every day a leetcode--118 together. Pascal ' s Triangle (Yang Hui triangle)

Given numrows, generate the first numrows of Pascal ' s triangle.

For example, given numrows = 5,
Return

[     1], [    1,2,1], [   1,3,3,1], [  1,4,6,4,1]

Solution:

ackage Cn.magicdu;Importjava.util.ArrayList;Importjava.util.List; Public class_118_pascal_triangle { PublicList<list<integer>> Generate (intnumrows) {        if(NumRows < 0) {            return NULL; } List<List<Integer>> L1 =NewArraylist<>(); if(NumRows >= 1) {List<Integer> list =NewArraylist<>(); List.add (1);        L1.add (list); }        if(NumRows >= 2) {List<Integer> list =NewArraylist<>(); List.add (1); List.add (1);        L1.add (list); }        if(NumRows >= 3) {             for(inti = 3; I <= numrows; i++) {List<Integer> list =NewArraylist<>(); List<Integer> prev = L1.get (i-2); List.add (1);  for(intj = 2; J <= I-1; J + +) {List.add (Prev.get (J-2) + Prev.get (j-1)); } list.add (1);            L1.add (list); }        }        returnL1; }}

Every day a leetcode--118 together. Pascal ' s Triangle (Yang Hui triangle)