# Leetcode 118. Pascal's Triangle
###### tags: `Leetcode`

題目
Given an integer numRows, return the first numRows of Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it as shown:

Example 1:

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

Input: numRows = 1
Output: [[1]]

解法:
1.用一個for圈代表rows，再根據每個row再用一個for迴圈，分別頭尾放1=>res[i][j] = 1;，中間的值就用計算的=>res[i][j] = res[i-1][j-1] + res[i-1][j];

註:
1. *(res+i) equal to res[i]
2. *(res)[i] equal to res[0][i]

/**
 * Return an array of arrays of size *returnSize.
 * The sizes of the arrays are returned as *returnColumnSizes array.
 * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
 */
int** generate(int numRows, int* returnSize, int** returnColumnSizes){
    if(numRows == 0)
        return 0;
    int** res = malloc(sizeof(int*)*numRows);
    *returnSize = numRows;
    *returnColumnSizes = malloc(sizeof(int)*numRows);
    
    for(int i = 0; i < numRows; i++)
    {
        *((*returnColumnSizes)+i) = i+1;
        *(res+i) = (int*)malloc(sizeof(int)*(i+1));
        for(int j = 0; j <= i; j++)
        {
            if(j == 0 || j == i)
                res[i][j] = 1;
            else
                res[i][j] = res[i-1][j-1] + res[i-1][j];
        }    
    }
    return res;
}