279. Perfect Squares

Problem Statement

Given an integer n, return the least number of perfect square numbers that sum to n.

A perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, 1, 4, 9, and 16 are perfect squares while 3 and 11 are not.

Example 1:

Input: n = 12
Output: 3
Explanation: 12 = 4 + 4 + 4.

Example 2:

Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.

Constraints:

1 <= n <= 10⁴

Solution:

Rust

use std::cmp::min;

impl Solution {
    pub fn num_squares(n: i32) -> i32 {
        // make a dp array of size n + 1 and filled with 0
        let mut dp = vec![n; n as usize + 1];

        // set the first element to 0
        dp[0] = 0;

        // iterate from 1 to n
        for i in 1..=n as usize {
            // iterate from 1 to sqrt(i)
            for j in 1..=(i as f64).sqrt() as usize {
                // set dp[i] to the minimum of dp[i] and dp[i - j * j] + 1
                dp[i] = min(dp[i], dp[i - j * j] + 1);
            }
        }

        dp[n as usize]
    }
}

279. Perfect Squares #

Problem Statement #

Solution: #

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279. Perfect Squares

Problem Statement

Solution:

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