区间dpP1063 能量项链

Posted 2021-12-02 pyyyyyy

一道区间dp的水题

题目链接

来快活啊！

思路

很简单的区间dp,思路和floyed差不多，就是需要把项链处理成环形

代码

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<map>
#include<string>
#include<cstring>

using namespace std;
inline int read() {
    char c = getchar();
    int x = 0, f = 1;
    while(c < '0' || c > '9') {
        if(c == '-') f = -1;
        c = getchar();
    }
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x * f;
}
int ans;
int f[1001][1001],n,a[10010];
signed main() {
    cin>>n;
    for(int i=1; i<=n; ++i) {
        cin>>a[i];
        a[n+i]=a[i];/*处理成环*/
    }
    for(int i=2; i<=n+1; ++i) {
        for(int l=1; l+i-1<=2*n/*注意应为2*n,因为上面处理成环了*/; ++l) {
            int r=l+i-1;
            for(int k=l+1; k<=l+i-2; ++k) {
                f[l][r]=max(f[l][r],f[l][k]+f[k][r]+a[l]*a[k]*a[r]);
            }
        }
    }
    for(int i=1; i<=n; ++i) {
        ans=max(ans,f[i][n+i]);
    }
    cout<<ans;
    return 0;
}