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.

动态规划的状态及转移过程（关键步骤）如下：

解题代码

class Solution {public:    int numSquares(int n) {        assert(n >= 1);        // memo[n] 表示以完全平方数分割n，最小的个数        vector<int> memo = vector<int>(n + 1, INT_MAX);        memo[0] = 0;        memo[1] = 1;        // 求解memo[i]        for (int i = 2; i <= n; i++){            for (int j = 1; j*j <= i; j++){                memo[i] = min(memo[i], 1 + memo[i - j*j]);            }        }        return memo[n];    }};

结果

求 [ 2912 ] 的完美平方, 结果为 ： 3请按任意键继续. . .