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.
方法1: 看作是01背包问题,用动态规划解决
class Solution { public int numSquares(int n) { int[] dp = new int[n+1]; for (int i=0; i<=n; i++) { dp[i] = i; for (int j = 0; j*j <= i; j++){ dp[i] = Math.min(dp[i], dp[i-j*j] + 1); } } return dp[n]; } }