每日一题：完全平方数

输入: n = 12输出: 3 解释: 12 = 4 + 4 + 4.

输入: n = 13输出: 2解释: 13 = 4 + 9.

输入 输出 解释n=1,  1,    1n=2,  2,    1,1n=3,  3,    1,1,1n=4,  1,    4n=5,  2,    4,1n=6,  3,    4,1,1n=7,  4,    4,1,1,1n=8,  2,    4,4n=9,  1,    9

dp[0]=0;dp[i]=min(dp[i-i之前的完全平方和]+1);

class Solution {public:    int numSquares(int n) {        vector<int> dp(n+1, INT_MAX);        dp[0] = 0;        for (int i = 1; i <=n; ++i) {            // 使用tem少进行一次乘法运算            for (int j = 1, tem = 0; tem = j * j, tem <= i; ++j) {                 dp[i] = min(dp[i], dp[i-tem] + 1);            }        }        return dp[n];    }};