楊輝三角：

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]
]

關於楊輝三角的意義具體可以百度。
本題很簡單，兩邊都是1，中間的各個元素等於其肩上的兩數之和。
很顯然用二維陣列可以很方便的處理，

/**
 * Return an array of arrays.
 * The sizes of the arrays are returned as *columnSizes array.
 * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
 */
 

int** generate(int numRows, int** columnSizes) {
    int **ret = (int **)malloc(sizeof(int *)*numRows);
    int *tmp = (int *)malloc(sizeof(int)*numRows);
    for(int i=0;i<numRows;i++)
    {
        ret[i] = (int *)malloc(sizeof(int)*(i+1));
        ret[i][0] = 1;
        ret[i][i] = 1;
        tmp[i] = i+1
 
;
        for(int j=1;j<i;j++)
            ret[i][j] = ret[i-1][j-1]+ret[i-1][j];
    }
    *columnSizes = tmp;
    return ret;
}