【codevs1048】石子归并

提交：http://codevs.cn/problem/1048/

递推

//f[i]:到i为止的LIS的长度。
//f[i]=max{1,f[j]+1|j<i&&aj<ai}
#include<iostream>
#include<algorithm>
using namespace std;
int n, a[510], f[510], ans;
int main(){
    cin>>n;
    for(int i = 1; i <= n; i++)cin>>a[i];
    for(int i = 1; i <= n; i++){
        int t = 0;
        for(int j = 1; j < i; j++)
            if(a[j]<a[i])t = max(t, f[j]);
        f[i] = t+1;
        ans = max(ans, f[i]);
    }
    cout<<ans<<"
";
    return 0;
}

递归

#include<iostream>
#include<algorithm>
using namespace std;
const int maxn = 1010, inf=0xffffff;
int w[maxn], f[maxn][maxn];
int dp(int i, int j){
    if(f[i][j] != inf)return f[i][j];
    for(int k = i; k <= j; k++)
        f[i][j] = min(f[i][j], dp(i,k)+dp(k+1,j)+w[j]-w[i-1]);
    return f[i][j];
}
int main(){
    int n;  cin>>n;
    for(int i = 1; i <= n; i++)cin>>w[i];
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++)
            f[i][j] = i==j ? 0 : inf;
    for(int i = 1; i <= n; i++)w[i] += w[i-1];
    cout<<dp(1,n)<<"
";
    return 0;
}