LeetCode: 279. Perfect Squares

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题目描述

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.

代码实现

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class Solution {
public:
    int numSquares(int n) {
        vector<int> dp(n+1);
        int element = 1;
        for (int i = 1; i <= n; i++) {
            dp[i] = i;
            if (pow(element+1, 2) <= i) {
                element += 1;
            }
            for (int j = 1; j <= element; j++) {
                dp[i] = min(dp[i], dp[i-pow(j, 2)] + 1);
            }
        }
        return dp[n];
    }
};