Leetcode-279. Perfect Squares

今天广州天气有点冷，如下图：

so，刷个题暖暖身吧！！看题：

279. Perfect Squares

 

Question Editorial Solution

  My Submissions

• Total Accepted: 56296
• Total Submissions: 163333
• Difficulty: Medium
• Contributors: Admin

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.

Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

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class Solution {
public:
	int numSquares(int n) {
		if (n < 1)return 0;
		vectordp(n+1,INT_MAX);
		for (int i = 1; i <= n; i++){
			int pro = i*i;
			if(pro<=n)dp[pro] = 1;
			else break;
		}
		for (int i = 2; i <= n;i++){
			if (dp[i] == 1)continue;
			int start = 1;
			while(start*start<=i){
				int temp = dp[i-start*start]+1;
				if (temp < dp[i])dp[i] = temp;
				start++;
			}
		}
		return dp[n];
	}
};

ubmission Result: Accepted  More Details 

Next challenges:  (E) Count Primes  (M) Ugly Number II

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解析：

题目不难，其实是01背包问题的拓展，有兴趣可以看看我的另外一篇博文：http://blog.csdn.net/caoyan_12727/article/details/52837081