Difficulty: Medium
Frequency: N/A
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
.
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class Solution { public: int numSquares(int n) { if (n <= 0) return -1; vector<int> countSquares(n + 1, INT_MAX); countSquares[0] = 0; for (int i = 1; i <= n; i++) { for (int j = 1; j * j <= i; j++) { countSquares[i] = min(countSquares[i], countSquares[i - j * j] + 1); } } return countSquares[n]; } };
Another solution:
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