Perfect Squares

Desicription

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:

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Input: n = 12
Output: 3 
Explanation: 12 = 4 + 4 + 4.

Example 2:

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Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.

Solution

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class Solution {
public:
    int numSquares(int n) {
        vector<int> dp(n+1, INT_MAX);
        dp[0] = 0;
        for(int i = 1, squares; (squares = i * i) <= n; i++) {
            for(int j = squares; j <= n; j++) {
                if(dp[j] > dp[j - squares] + 1) {
                    dp[j] = dp[j - squares] + 1;
                }
            }
        }
        return dp[n];
    }
};