poj2184 Cow Exhibition

01背包的變形，需要注意的地方很多。

很炫的代碼來自這位大神http://www.cnblogs.com/rainydays/archive/2012/07/04/2576077.html

代碼很高效，邊界控制很值得學習

#include<iostream>#include<cstdio>#include<cstring>#define INF 0x3f3f3f3f#define maxs 2000*100#define shift 1000*100using namespace std;int dp[maxs],s[105],f[105];int main(){int n;int i,j;scanf("%d",&n);for(i=0;i<n;i++)scanf("%d%d",&s[i],&f[i]);for(i=0;i<maxs;i++)dp[i]=-INF;dp[0+shift]=0;int l=0,r=0;for(i=0;i<n;i++){l=min(l,l+s[i]);r=max(r,r+s[i]);int step=1;int begin=l,end=r;if(s[i]>0){step=-1;swap(begin,end);}for(j=begin;j!=end+step;j+=step)dp[j+shift]=max(dp[j-s[i]+shift]+f[i],dp[j+shift]);}int ans=0;for(i=0;i<=r;i++)if(dp[i+shift]>=0)ans=max(ans,i+dp[i+shift]);printf("%d\n",ans);return 0;}