322. Coin Change(C++实现)

class Solution {

int *dp;
vector<int> a;

int dfs(int S)
{
if(dp[S]!=-2) return dp[S];

int ans=-1;

for(int i=0;i<a.size();i++)
{
const int w=a[i];
if(S<w) continue;

int tmp=dfs(S-w);
if(tmp!=-1)
{
tmp+=1;
if(ans==-1||ans>tmp) ans=tmp;
}
}
return dp[S]=ans;
}

public:

int coinChange(vector<int>& coins, int amount)
{
if(amount==0)return 0;
dp=new int[amount+1];
for(int i=0;i<=amount;i++) dp[i]=-2;
dp[0]=0;
a=coins;
return dfs(amount);

}
};

class Solution {
public:

int coinChange(vector<int>& coins, int amount) {
if(amount==0)return 0;

const int n=coins.size();

int *dp=new int[amount+1];
memset(dp,-1,sizeof(int)*(amount+1));
dp[0]=0;
for(int i=0;i<n;i++)
{
const int w=coins[i];
for(int i=amount;i>=0;i--) if(dp[i]!=-1)
{
for(int j=1;i+j*w<=amount;j++)
{
int k=i+j*w;
if(dp[k]==-1||dp[k]>dp[i]+j) dp[k]=dp[i]+j;
}
}
}

return dp[amount];
}
};