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pascal_triangle.cpp
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pascal_triangle.cpp
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// =====================================================================================
//
// Filename: pascal_triangle.cpp
//
// Description: 118. Pascal's Triangle.
// Given a non-negative integer numRows, generate the first numRows of
// Pascal's triangle. In Pascal's triangle, each number is the sum of
// the two numbers directly above it.
//
// Version: 1.0
// Created: 08/16/2019 11:46:07 AM
// Revision: none
// Compiler: g++
//
// Author: Zhu Xianfeng (), [email protected]
// Organization:
//
// =====================================================================================
#include <stdio.h>
#include <stdlib.h>
#include <vector>
using std::vector;
// Non-recursive
class Solution1
{
public:
vector<vector<int>> generate(int rows)
{
vector<vector<int>> nums;
for (int i = 0; i < rows; i++)
{
nums.push_back(vector<int>(i + 1, 0));
nums[i][0] = 1;
if (i < 1)
{
continue;
}
nums[i][i] = 1;
for (int j = 1; j < i; j++)
{
nums[i][j] = nums[i - 1][j - 1] + nums[i - 1][j];
}
}
return nums;
}
};
// Recursive
class Solution2
{
public:
vector<vector<int>> generate(int rows)
{
vector<vector<int>> nums(rows, vector<int>());
for (int i = 0; i < rows; i++)
{
nums[i].resize(i + 1);
}
if (rows > 0)
{
nums[0][0] = 1;
}
for (int i = 0; i < rows; i++)
{
nums[rows - 1][i] = generate(nums, rows - 1, i);
}
return nums;
}
private:
int generate(vector<vector<int>>& nums, int i, int j)
{
if (nums[i][j] != 0)
{
return nums[i][j];
}
if (i == 0 || j == 0 || i == j)
{
nums[i][j] = 1;
}
else
{
nums[i][j] = generate(nums, i - 1, j - 1) + generate(nums, i - 1, j);
}
return nums[i][j];
}
};
using Solution = Solution2;
int main(int argc, char* argv[])
{
int rows = 6;
if (argc > 1)
{
rows = atoi(argv[1]);
}
auto nums = Solution().generate(rows);
for (const auto& row: nums)
{
for (const auto& item: row)
{
printf("%d ", item);
}
printf("\n");
}
return 0;
}