CCF 压缩编码（石子合并问题）

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#include<iostream>#include<cstdio>#include<cstring>#include<vector>#include<algorithm>#include<cmath>#include<queue>#include<map>#include<stack>#include<set>using namespace std;typedef long long ll;const int maxn=300010;int n,m;int a[1010];int dp[1010][1010];int sum[1010];int main(){    cin>>n;for(int i=1;i<=n;++i){cin>>a[i];sum[i]=sum[i-1]+a[i];}if(n==1){cout<<a[1]<<endl;return 0;}if(n==2){cout<<a[1]+a[2]<<endl;return 0;}for(int i=1;i<n;++i){dp[i][i+1]=a[i]+a[i+1];}for(int len=3;len<=n;++len){for(int i=1;i+len-1<=n;++i){int j=i+len-1;dp[i][j]=0xfffffff;for(int k=i;k<=j;++k){dp[i][j]=min(dp[i][j],dp[i][k]+dp[k+1][j]+sum[j]-sum[i-1]);}}}cout<<dp[1][n]<<endl;        return 0;}

四边形不等式优化;

#include<iostream>#include<cstdio>#include<cstring>#include<vector>#include<algorithm>#include<cmath>#include<queue>#include<map>#include<stack>#include<set>using namespace std;typedef long long ll;const int maxn=1010;const int inf=0xfffffff;int n;int a[maxn];int dp[maxn][maxn];int sum[maxn];int p[maxn][maxn];int main(){    int i,j,k;while(~scanf("%d",&n)){for(i=1;i<=n;++i){scanf("%d",&a[i]);sum[i]=sum[i-1]+a[i];p[i][i]=i;dp[i][i]=0;}if(n==1){printf("%d\n",a[1]);continue;}if(n==2){printf("%d\n",a[1]+a[2]);continue;}int len;for(len=2;len<=n;++len){for(i=1;i+len-1<=n;++i){j=i+len-1;dp[i][j]=inf;for(k=p[i][j-1];k<=p[i+1][j];++k){int s=dp[i][k]+dp[k+1][j]+sum[j]-sum[i-1];if(s<dp[i][j]){dp[i][j]=s;p[i][j]=k;}}}}printf("%d\n",dp[1][n]);sum[0]=0;}    return 0;}

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