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  • 118. Pascal's Triangle

    118. Pascal's Triangle

    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]
    ]


    public class Solution {
        /*
        public List<List<Integer>> generate(int numRows) {
            List<List<Integer>> res = new ArrayList<>();
            if(numRows == 0) return res;
            List<Integer> member = new ArrayList<>();
            member.add(1);
            res.add(member);
            if(numRows == 0) return res;
            for(int i = 1; i< numRows ; i++){
                List<Integer> newMember = new ArrayList<>();
                newMember.add(1);
                for(int j = 0; j < member.size() -1; j ++){
                    newMember.add(member.get(j) + member.get(j+1));
                }
                newMember.add(1);
                res.add(newMember);
                member = newMember;
            }
            return res;
        } */
        
    
        //   better way
        //    set(int index, E element)  Replaces the element at the specified position in this list with the specified element (optional operation).
        
         public List<List<Integer>> generate(int numRows) {
            List<List<Integer>> res = new ArrayList<>();
            if(numRows == 0) return res;
            List<Integer> member = new ArrayList<>();
            for(int i = 0; i< numRows ; i++){
                member.add(0,1); //每次在首度加1
                for(int j = 1 ; j < member.size() -1 ; j++){
                    member.set(j, member.get(j) + member.get(j +1));
                }
                System.out.println(member);
                res.add(new ArrayList<Integer> (member));
            }
            return res;
         }
    }
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  • 原文地址:https://www.cnblogs.com/joannacode/p/5966532.html
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