29 lines
774 B
C++
29 lines
774 B
C++
#include<cstdio>
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#include<cstring>
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#include<algorithm>
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using namespace std;
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typedef long long LL;
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const int maxn=55;
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int n,c,p[maxn],w[maxn];
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LL s[maxn],f[maxn][maxn][2];
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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scanf("%d%d",&n,&c);
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for(int i=1;i<=n;i++) scanf("%d%d",&p[i],&w[i]);
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for(int i=1;i<=n;i++) s[i]=s[i-1]+w[i];
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memset(f,0x3f,sizeof(f));
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f[c][c][0]=f[c][c][1]=0;
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for(int len=1;len<n;len++)
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for(int i=1;i+len-1<=n;i++)
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{
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int j=i+len-1;
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LL W=s[i-1]+s[n]-s[j];
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if(i>1) f[i-1][j][0]=min(f[i-1][j][0],min(f[i][j][0]+(p[i]-p[i-1])*W,f[i][j][1]+(p[j]-p[i-1])*W));
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if(j<n) f[i][j+1][1]=min(f[i][j+1][1],min(f[i][j][0]+(p[j+1]-p[i])*W,f[i][j][1]+(p[j+1]-p[j])*W));
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}
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printf("%lld\n",min(f[1][n][0],f[1][n][1]));
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return 0;
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} |