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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++

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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。。。

请我喝杯咖啡吧~