leetcode-java-279. Perfect Squares

public class Solution {
     public int numSquares(int n) {
         int[] dp = new int[n+1];
        //  确保后边选min的正确
         Arrays.fill(dp,Integer.MAX_VALUE);

         for(int i = 0;i*i <= n;i++) {
             dp[i*i] = 1;
         }
        //  从小到大找整数i
         for(int i = 0;i <= n;i++) {
            //  从小到大找平方数j*j
             for(int j = 1;i+j*j <= n;j++) {
                 dp[i +j * j] = Math.min(dp[i]+1,dp[i+j*j]);
             }
         }
         return dp[n];
     }
 }