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leetcode 118. pascal’s triangle

admin 11月 13, 2020 0

118. Pascal’s Triangle

Difficulty: Easy

Given a non-negative integer numRows, generate the first numRows of Pascal’s triangle.

In Pascal’s triangle, each number is the sum of the two numbers directly above it.

Example:

Input: 5
Output:
[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

Solution

Language: Java

class  {
      public List<List<Integer>> generate(int numRows) {
            List<List<Integer>> result = new ArrayList<>();
            if (numRows <= 0) {
                  return result;
           }
            for (int i = 0; i < numRows; i++) {
                  List<Integer> line = new ArrayList<>();
                  for (int j = 0; j <= i; j++) {
                        if (j == 0 || j == i) {
                              line.add(1);
                              continue;
                       }
                        line.add(result.get(i - 1).get(j - 1) + result.get(i - 1).get(j));
                 }
                  result.add(line);
           }
            return result;
     }
}