POJ #2479 - Maximum sum

Hi, I'm back.

This is a realy classic DP problem to code.

1. You have to be crystal clear about what you are going to solve.
2. Apparently there are 2 DP sections
3. Think carefully about recurrence relations
5. Details: take care of indices boundaries - it costed me 1hr to find an indexing bug!
6. Again: think crystal clear before you code!

And, #2593 is exactly the same.

Here is my AC code:

 #include <stdio.h>

 #define MAX_INX 50010
 #define Max(a,b) (a)>(b)?(a):(b)

 int max_sum2(int *pData, int cnt)
 {
     //    DP: Max sum of sub-sequence: dp[i] = MAX(num[i], dp[i-1] + num[i])

     //    Left -> Right
     int  lt[MAX_INX] = {  };
     lt[] = pData[];
     for (int i = ; i < cnt; i ++)
     {
         lt[i] = Max(pData[i], lt[i - ] + pData[i]);
     }

     //    Right -> Left
     int   rt[MAX_INX] = {  };
     int     rtm[MAX_INX] = {  };
     rt[cnt-] = pData[cnt-];
     for (int i = cnt-; i >= ; i--)
     {
         rt[i] = Max(pData[i], rt[i + ] + pData[i]);
     }
     rtm[cnt-] = rt[cnt-];
     for (int i = cnt-; i >=; i--)
     {
         rtm[i] = Max(rtm[i+], rt[i]);
     }

     //    O(n) to find real max
     int ret = -;
     for (int i = ; i < cnt - ; i ++)
     {
         ret = Max(ret, lt[i] + rtm[i+]);
     }

     return ret;
 }

 int main()
 {
     int nTotal = ;
     scanf("%d", &nTotal);

     while (nTotal--)
     {
         int num[MAX_INX] = {  };

         //    Get Input
         int nCnt = ; scanf("%d", &nCnt);
         for (int i = ; i < nCnt; i ++)
         {
             scanf("%d", num + i);
         }

         printf("%d\n", max_sum2(num, nCnt));
     }

     return ;
 }