leecode_279 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

.

bfs内存爆了，还是用dp吧

class Solution {
public:
int numSquares(int n) {
const int len=n+1;
int res[len];
for (int i=0;i<len;i++)
res[i]=INT_MAX;
for (int i=1;i*i<=n;i++)
res[i*i]=1;

for (int i=1;i<=n;i++) {

for (int j=1;j*j<=i;j++){
if (i+j*j>n)
break;
if (i+j*j<=n ){
res[i+j*j]=min(res[i]+1,res[i+j*j]);

}
}

}

// for (int i=1;i<=n;i++)
// cout<<i<<"("<<res[i]<<")"<<" ";
// cout<<endl;

return res
;

}
};