Pascals triangle

Array Dynamic Programming

78.7% acceptance

Jan 12, 2026

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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:

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn generate(num_rows: i32) -> Vec<Vec<i32>> {
    let mut result: Vec<Vec<i32>> = Vec::with_capacity(num_rows as usize);
    
    for i in 0..num_rows as usize {
      let mut row = Vec::with_capacity(i + 1);
      row.push(1);
      
      if i > 0 {
        let prev = &result[i - 1];
        for j in 0..prev.len() - 1 {
          row.push(prev[j] + prev[j + 1]);
        }
        row.push(1);
      }
      
      result.push(row);
    }
    
    result
  }
}