leetcode Perfect Squares

leetcode 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.

题目地址： leetcode Perfect Squares

题意： 给定一个整数n，找到最少的完全平方数使得他们的和为n

思路：

dp,设dp[i]为和i的最少完全平方数。

dp[i] = min(dp[i - j*j] + 1) {j *j <i}

code

C++

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

Python同样的代码会超时。。。