题目:
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
.
思路:
转移方程:dp[i] = min(dp[i],1 + dp[i - j * j])。
程序:
class Solution {
public:
int numSquares(int n) {
vector<int> dp(n + 1,INT_MAX);
dp[0] = 0;
for(int i = 1;i <= n;i++)
{
for(int j = 1;j * j <= i;j++)
dp[i] = min(dp[i],1 + dp[i - j * j]);
}
return dp[n];
}
};