比较明显的dp了=
dp[i][j][flag]前i个栅栏中，红/绿颜料用了j的最小接触值
具体转移见程序：
1 #include<stdio.h> 2 #include<string.h> 3 #include<algorithm> 4 using namespace std; 5 int dp[225][45005][2],a[225]; 6 int main() 7 { 8 int n,x,y,i,j,tmp=0,minx; 9 freopen("input.txt","r",stdin); 10 freopen("output.txt","w",stdout); 11 scanf("%d%d%d",&n,&x,&y); 12 for (i=1;i<=n;i++) scanf("%d",&a[i]); 13 memset(dp,0x3f,sizeof(dp)); 14 dp[0][0][0]=dp[0][0][1]=a[0]=0; 15 for (i=1;i<=n;i++){ 16 tmp+=a[i]; 17 for (j=a[i];j<=tmp;j++){ 18 if (j<=x){ 19 dp[i][j][0]=min(dp[i-1][j-a[i]][0], 20 dp[i-1][tmp-j][1]+min(a[i],a[i-1])); 21 } 22 if (j<=y){ 23 dp[i][j][1]=min(dp[i-1][j-a[i]][1], 24 dp[i-1][tmp-j][0]+min(a[i],a[i-1])); 25 } 26 } 27 } 28 minx=0x3f3f3f3f; 29 for (i=0;i<=x;i++) 30 minx=min(minx,dp[n][i][0]); 31 for (i=0;i<=y;i++) 32 minx=min(minx,dp[n][i][1]); 33 if (minx==0x3f3f3f3f) printf("-1\n"); 34 else printf("%d\n",minx); 35 return 0; 36 }