|
| 1 | + |
| 2 | +# Pascal's Triangle - LeetCode Solution 🚀 |
| 3 | + |
| 4 | +## Problem Statement |
| 5 | +Given an integer `numRows`, return the first `numRows` of Pascal's triangle. |
| 6 | + |
| 7 | +## Approach |
| 8 | + |
| 9 | +To generate Pascal's Triangle, follow these steps: |
| 10 | + |
| 11 | +1. **Initialization**: |
| 12 | + - Create a 2D vector `result` to store the rows of Pascal's Triangle. |
| 13 | + |
| 14 | +2. **Iterate through the rows**: |
| 15 | + - Loop from `0` to `numRows - 1` to generate each row. |
| 16 | + - For each row `i`, initialize a vector `row` with `i + 1` elements, all set to `1` because the first and last elements of each row are always `1`. |
| 17 | + |
| 18 | +3. **Fill in the values**: |
| 19 | + - For each element `j` in the row, except for the first and last elements, set `row[j]` to the sum of the two elements directly above it from the previous row: |
| 20 | + \[ |
| 21 | + row[j] = result[i - 1][j - 1] + result[i - 1][j] |
| 22 | + \] |
| 23 | + |
| 24 | +4. **Add the row to the result**: |
| 25 | + - Append the fully populated row to the `result` vector. |
| 26 | + |
| 27 | +5. **Return the result**: |
| 28 | + - After generating all rows, return the `result` vector. |
| 29 | + |
| 30 | +### Time Complexity ⏱️ |
| 31 | +- The time complexity is **O(numRows^2)** because we are iterating through each element of each row once. |
| 32 | + |
| 33 | +### Space Complexity 💾 |
| 34 | +- The space complexity is **O(numRows^2)** due to the space required to store the entire triangle in memory. |
| 35 | + |
| 36 | +## Code Implementation in C++ |
| 37 | + |
| 38 | +```cpp |
| 39 | +class Solution { |
| 40 | +public: |
| 41 | + vector<vector<int>> generate(int numRows) { |
| 42 | + std::vector<std::vector<int>> result; |
| 43 | + for(int i=0; i < numRows; i++){ |
| 44 | + std::vector<int> row(i + 1, 1); |
| 45 | + for(int j = 1; j < i; j++){ |
| 46 | + row[j] = result[i - 1][j - 1] + result[i - 1][j]; |
| 47 | + } |
| 48 | + result.push_back(row); |
| 49 | + } |
| 50 | + return result; |
| 51 | + } |
| 52 | +}; |
| 53 | +``` |
| 54 | +
|
| 55 | +### LeetCode Performance 💯 |
| 56 | +- **Time Complexity**: `0ms` (As fast as possible) |
| 57 | +- **Space Complexity**: `0ms` (Optimal memory usage) |
| 58 | + |
| 59 | +> 🚀 **Conclusion**: This solution efficiently generates Pascal's Triangle with minimal time and space complexity. Enjoy coding! |
| 60 | +
|
| 61 | +--- |
| 62 | +
|
| 63 | +**Keep Coding!** 💻✨ |
0 commit comments