[LeetCode] 118. Pascal's Triangle

• Problem: 118 Pascals's Triangle, 主要為該層元素為上一層的左邊加上一層右邊而得
• Concept:
• 算是滿基本的題目, 稍微將 index 列出來, 可以發現

• A[i][j] = A[i-1][j-1] + A[i-1][j]

• 但還是需要注意 index 從 0開始, 必須習慣一下
• Implementation

• class Solution {
  public:
      vector> generate(int numRows) {
          vector> result;
  
          for (int i = 0; i < numRows; i++) {
              vector row;
              
              row.push_back(1);
              for (int j = 1; j < i; j++) {
                  int val = result[i - 1] [j - 1] + result[i - 1][j];
                  row.push_back(val);
              }
              // no need to add right 1 at first row
              if (i > 0) row.push_back(1);
              
              result.push_back(row);
          }
          return result;
      }
  };