poj 2228

要注意边界条件的判断(第一次写的麻烦了。。)

# include <cstdio>
# include <cstring>
# include <iostream>
# define inf 0x8fffffff;
using namespace std;
int max(int a,int b)
{
    return a>b?a:b;
}
int dp[2][4000][2],v[4000];
int main()
{
    int n,b,i,j,ans = 0;
    scanf("%d%d",&n,&b);
    for (i=1;i<=n;++i)
        scanf("%d",&v[i]);
    memset(dp,0,sizeof(dp));
    dp[1][1][0] = inf;
    for (i=2;i<=n;++i)
        for (j=0;j<b;++j)
        {
            dp[i%2][j][1] = max(dp[(i-1)%2][j-1][0],dp[(i-1)%2][j-1][1]+v[i]);
            dp[i%2][j][0] = max(dp[(i-1)%2][j][0],dp[(i-1)%2][j][1]);
            if (!j) dp[i%2][j][1] = inf;
        }
    ans = max(dp[n%2][b-1][0],dp[n%2][b-1][1]+v[1]);
        
    memset(dp,0,sizeof(dp));
    dp[0][0][1] = inf;
    for (i=3;i<=n;++i)
        for (j=0;j<=b;++j)
        {
            dp[i%2][j][1] = max(dp[(i-1)%2][j-1][0],dp[(i-1)%2][j-1][1]+v[i]);
            dp[i%2][j][0] = max(dp[(i-1)%2][j][0],dp[(i-1)%2][j][1]);
            if (!j) dp[i%2][j][1] = inf;
        }
    ans = max(ans,max(dp[n%2][b][1],dp[n%2][b][0]));
    printf("%d
",ans);
    return 0;
}