55分求助

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N=1e3+10;
int a[N],b[N];
int f[N][N*6];
int n;
int s[N];
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++){cin>>a[i]>>b[i];s[i]=s[i-1]+a[i]+b[i];}
    memset(f,100,sizeof f);
    f[0][0]=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=s[i];j++){
            f[i][j]=min(f[i-1][j-a[i]],f[i-1][j-b[i]]+1);
        }
    }
    int ans=1e9,sum=1e9;
    for(int i=1;i<=s[n];i++){
        if(f[n][i]<=1000000){
            if(abs(s[n]-i-i)<sum){
                sum=abs(s[n]-i-i);
                ans=f[n][i];    
            }
            if(abs(s[n]-i-i)==sum)ans=min(ans,f[n][i]);
        }
    }
    cout<<ans;
}