pascal's_triangle.md

Pascal's Triangle

杨辉三角形

Problem

Given numRows, generate the first numRows of Pascal's triangle.

分析

杨辉三角形的规律都知道，那就只要注意代码的注释中动态内存分配就可以了

代码实现

/**
 * 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 i=0;    
    int j=0;
    if(numRows==0)
        return 0;
    int ** returnArray = (int **)malloc(sizeof(int *) * numRows);
    *columnSizes = (int *)malloc(sizeof(int)*numRows);
    for(i=0;i<numRows;i++)
    {
        (*columnSizes)[i] = i+1;
        returnArray[i] = (int *)malloc(sizeof(int) * (i+1));
        for(j=0; j<i+1; j++)
        {
            if( (0==j)  || (i == j) )
                returnArray[i][j] = 1;
            else
                returnArray[i][j] = returnArray[i-1][j-1] + returnArray[i-1][j];
        }
    }
    return returnArray;
}