lintcode-medium-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.

 

Example

Given n = 12, return 3 because 12 = 4 + 4 + 4
Given n = 13, return 2 because 13 = 4 + 9

 

public class Solution {
    /**
     * @param n a positive integer
     * @return an integer
     */
    public int numSquares(int n) {
        // Write your code here
        
        if(n <= 0)
            return 0;
        
        int[] dp = new int[n + 1];
        dp[0] = 0;
        
        for(int i = 1; i <= n; i++)
            dp[i] = i;
        
        for(int i = 0; i <= n; i++){
            for(int j = 1; i + j * j <= n; j++){
                dp[i + j * j] = Math.min(dp[i + j * j], dp[i] + 1);
            }
        }
        
        return dp[n];
    }
}