Problem

Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, ...) which sum to n.

Example 1:

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

Example 2:

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

Code

public class Solution {
    
    public int numSquares(int n) {
        int t = (int) Math.sqrt(n);
        int[] dp = new int[n + 1];
        for (int i = 1; i <= n; ++i) {
            dp[i] = Integer.MAX_VALUE;
        }
        for (int i = 1; i <= t; ++i) {
            int m = i * i;
            for (int j = 1; j <= n; ++j) {
                if (j >= m && dp[j] > dp[j - m] + 1) {
                    dp[j] = dp[j - m] + 1;
                }
            }
        }
        return dp[n];
    }
    
}

Link: https://leetcode.com/problems/perfect-squares/