Leetcode 279: Perfect Squares

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

For example, given n = 12, return 3 because 12 = 4 + 4 + 4; given n = 13, return 2 because 13 = 4 + 9.

 

public class Solution {
    public int NumSquares(int n) {
        var dp = new int[n + 1];
        dp[0] = 0;
        
        for (int i = 1; i <= n; i++)
        {
            dp[i] = Int32.MaxValue;
            for (int j = 1; j <= i / j; j++)
            {
                dp[i] = Math.Min(dp[i], dp[i - j * j] + 1);
            }
        }
        
        return dp[n];
    }
}