Perfect Squares
Total Accepted: 18854 Total Submissions: 63048 Difficulty: Medium
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.
dp
f(n) = min{f(n-1),f(n-4),f(n-9)...f(n-k*k)}+1,其中k*k <=n && k>=1;
class Solution {
public:
int numSquares(int n) {
vector<int> dp(n+,);
for(int i=;i<=n;i++){
int k = INT_MAX ,j=;
while(j*j <= i){
k = min(k,dp[i-j*j]+);
j++;
}
dp[i] = k;
}
return dp.back();
}
};