Algorithm
Problem Nmae: 118. Pascal's Triangle
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]]
Constraints:
1 <= numRows <= 30
Code Examples
#1 Code Example with C Programming
Code -
C Programming
int** generate(int numRows, int** columnSizes) {
int i, j;
int *buff, **p;
p = malloc(numRows * sizeof(int *));
*columnSizes = malloc(numRows * sizeof(int));
//assert(p && *columnSizes);
for (i = 1; i < = numRows; i ++) {
buff = malloc(i * sizeof(int));
//assert(buff);
p[i - 1] = buff;
(*columnSizes)[i - 1] = i;
buff[0] = 1;
for (j = 1; j < i - 1; j ++) {
buff[j] = p[i - 2][j - 1] + p[i - 2][j];
}
buff[i - 1] = 1;
}
return p;
}
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Output
#2 Code Example with C++ Programming
Code -
C++ Programming
class Solution {
public:
vector<vector<int>> generate(int numRows) {
if(numRows == 0) return {};
if(numRows == 1) return {{1}};
auto v = generate(numRows - 1);
auto lastRow = *(v.end() - 1);
vector<int>res(1, 1);
for(int i = 0; i < lastRow.size() - 1; i++) res.push_back(lastRow[i] + lastRow[i + 1]);
res.push_back(1);
v.push_back(res>;
return v;
}
};
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Output
#3 Code Example with Java Programming
Code -
Java Programming
class Solution {
public List();
for (int i = 0; i < numRows; i++) {
List temp = new ArrayList<>();
for (int j = 0; j < = i; j++) {
temp.add(
(j == 0 || j == i) ? 1 :
(result.get(i - 1).get(j - 1) + result.get(i - 1).get(j)));
}
result.add(temp);
}
return result;
}
}
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Output
#4 Code Example with Javascript Programming
Code -
Javascript Programming
const generate = function(numRows) {
// row 0 => [1] length 0
// row 1 => [1, 1] length 1
// row 2 => [1, 2, 1] length 2
// row 3 => [1, 3, 3, 1] length 3
// current[i] = prev[i - 1] + prev[i]
const res = [];
for (let row = 0; row < numRows; row += 1) {
if (row === 0) {
res.push([1]);
continue;
}
if (row === 1) {
res.push([1, 1]);
continue;
}
const newRow = [];
const maxIdx = row;
for (let i = 0; i < = maxIdx; i += 1) {
if (i === 0 || i === maxIdx) {
newRow.push(1);
} else {
newRow.push(res[row - 1][i - 1] + res[row - 1][i]);
}
}
res.push(newRow);
}
return res;
};
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Output
#5 Code Example with Python Programming
Code -
Python Programming
class Solution:
def generate(self, numRows: int) -> List[List[int]]:
res = numRows and [[1]] or []
for _ in range(numRows-1):
res.append([1] + [a + b for a, b in zip(res[-1], res[-1][1:])] + [1])
return res
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Output
#6 Code Example with C# Programming
Code -
C# Programming
using System.Collections.Generic;
namespace LeetCode
{
public class _118_PascalsTriangle
{
public IList < IList<int>> Generate(int numRows)
{
var results = new List < IList<int>>();
if (numRows < = 0) return results;
results.Add(new List<int>(1) { 1 });
if (numRows == 1) return results;
results.Add(new List < int>(2) { 1, 1 });
if (numRows == 2) return results;
for (int i = 2; i < numRows; i++)
{
var result = new List<int>(i + 1);
result.Add(1);
for (int j = 1; j < i; j++)
{
result.Add(results[i - 1][j - 1] + results[i - 1][j]);
}
result.Add(1);
results.Add(result);
}
return results;
}
}
}
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Output