P1282 多米诺骨牌 76分 WA on #7#8#9 求调在线急

#include<bits/stdc++.h>
using namespace std;
const int N=1005,INF=0x3f3f3f3f;
int a[N],dp[N][2*N];
int main(){
	int n;
	cin >> n;
	memset(dp,0x3f,sizeof(dp));
	dp[0][N]=0;
	for(int i=1,x,y;i<=n;i++){
		cin >> x >> y;
		a[i]=x-y;
	}
	for(int i=1;i<=n;i++)
		for(int t=0;t<=2*N;t++)
			if(dp[i-1][t]<INF){
				if(t+a[i]>=0&&t+a[i]<=2*N) dp[i][t+a[i]]=min(dp[i][t+a[i]],dp[i-1][t]);
				if(t-a[i]>=0&&t-a[i]<=2*N) dp[i][t-a[i]]=min(dp[i][t-a[i]],dp[i-1][t]+1);
			}
	int t1=N,t2=N;
	for(;t1>=0;t1--) if(dp[n][t1]<INF) break;
	for(;t2<=2*N;t2++) if(dp[n][t2]<INF) break;
	if(N-t1==t2-N) cout << min(dp[n][t1],dp[n][t2]) << "\n";
	else if(N-t1<t2-N) cout << dp[n][t1] << "\n";
	else cout << dp[n][t2] << "\n";
	return 0;
}