[LeetCode][JavaScript]Pascal's Triangle

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]
]

https://leetcode.com/problems/pascals-triangle/

 

 

 

 

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杨辉三角。

每行第一个和最后一个是1，其余是pre[i - 1] + pre[i]。

/**
 * @param {number} numRows
 * @return {number[][]}
 */
var generate = function(numRows) {
    var res = [], count = 0, row;
    while(numRows--){
        row = [1];
        if(count !== 0){
            pre = res[count - 1];
            for(i = 1; i < count; i++){
                row.push(pre[i - 1] + pre[i]);
            }
            row.push(1);
        }
        res.push(row);
        count++;
    }
    return res;
};