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 <= 104struct Solution;
impl Solution {
fn num_squares(n: i32) -> i32 {
let n = n as usize;
let mut dp = vec![std::usize::MAX; n + 1];
dp[0] = 0;
for i in 1..=n {
let mut j = 1;
while j * j <= i {
dp[i] = dp[i].min(dp[i - j * j] + 1);
j += 1;
}
}
dp[n] as i32
}
}
#[test]
fn test() {
let n = 12;
let res = 3;
assert_eq!(Solution::num_squares(n), res);
let n = 13;
let res = 2;
assert_eq!(Solution::num_squares(n), res);
}