acwing282.石子合并【区间dp】

#include "bits/stdc++.h"
using namespace std;
#define int long long
#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
int n;
int dp[305][305];       //记录区间最小
int num[305];           //数列
int pre[305];           //前缀和
inline int sum(int l,int r){    //求区间和
    return pre[r] - pre[l];
}
signed main(){
    IOS
    memset(dp,0x3f,sizeof dp);
    cin>>n;
    for(int i = 1;i <= n;++i)
        cin>>num[i],pre[i] = pre[i - 1] + num[i],dp[i][i] = 0;
    for(int i = 2;i <= n;++i)   //合并后的长度为2...n
        for(int l = 1,k = n - i + 1;l <= k;++l) //合并后起点为l，并且起点可以是1 ~ n-i+1
            for(int p = l,r = l + i - 1;p < r;++p)
                dp[l][r] = min(dp[l][p] + dp[p + 1][r] + sum(l - 1,r),dp[l][r]);
    int ans = dp[1][n];
    cout<<ans;
    return 0;
}