HDU

HDU - 2829

思路：

平形四边形不等式优化dp

同上一篇博客

代码：

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize(4)
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define y1 y11
#define fi first
#define se second
#define pi acos(-1.0)
#define LL long long
#define LD long double
//#define mp make_pair
#define pb push_back
#define ls rt<<1, l, m
#define rs rt<<1|1, m+1, r
#define ULL unsigned LL
#define pll pair<LL, LL>
#define pli pair<LL, int>
#define pii pair<int, int>
#define piii pair<int, pii>
#define pdd pair<long double, long double>
#define mem(a, b) memset(a, b, sizeof(a))
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//head

const int N = 1e3 + 5;
LL dp[N][N], w[N][N];
int n, m, s[N][N], a[N];
int main() {
    while(~scanf("%d %d", &n, &m) && n && m) {
        for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
        for (int i = 0; i <= m+1; ++i) for (int j = 0; j <= n; ++j) dp[i][j] = 1LL<<58;
        for (int i = 1; i <= n; ++i) {
            w[i][i] = 0;
            int s = a[i];
            for (int j = i+1; j <= n; ++j) {
                w[i][j] = w[i][j-1]+s*a[j];
                s += a[j];
            }
        }
        dp[0][0] = 0;
        for (int i = 1; i <= m+1; ++i) {
            w[i][n+1] = n-1;
            for (int j = n; j >= 1; --j) {
                for (int k = w[i-1][j]; k <= w[i][j+1]; ++k) {
                    if(k+1 <= j && dp[i-1][k]+w[k+1][j] < dp[i][j]) {
                        dp[i][j] = dp[i-1][k]+w[k+1][j];
                        w[i][j] = k;
                    }
                }
            }
        }
        printf("%d
", dp[m+1][n]);
    }
    return 0;
}