Maximum and subsequence Problems

Source: Internet
Author: User

// Hhh. cpp: defines the entry point of the console application.

# Include "stdafx. H"
# Include <iostream>

Using namespace STD;

Int maxsub_sum (const int A [], int N, Int & seqstart, Int & seqend)
Int thissum, maxsum, I, j;
Thissum = 0;
Maxsum = 0;
I = 0;
From left to right. If the result is continuously increasing, thissum and maxsum will increase together.
If a negative number is encountered, it is also added to thissum. In this case, thissum <maxsum is not added to maxsum.
Check whether thissum will recover. If thissum does not continue to recover, it will not or the ripple will fall.
If it falls to 0, the previous rising and falling stages can be abandoned and a new stage starts. At this time, thissum = 0,
However, maxsum retains the maximum value of the previous rising phase.
Then, thissum starts to analyze the new sub-segments. If there are sub-segments larger than the current maxsum, replace them. (Maxsum in the previous rising stage will be completely discarded)
The time complexity is O (n)

For (j = 0; j <n; j ++)
Thissum + = A [J];
If (thissum> maxsum)
Maxsum = thissum;
Seqstart = I;
Seqend = J;
Else if (thissum <0)
I = J + 1;
Thissum = 0;

Return maxsum;

Int _ tmain (INT argc, _ tchar * argv [])
Int A [] = {1, 2,-1, 1, 3, 2,-2, 3,-1, 5,-7, 3, 2,-2, -1 };
Int size = sizeof (a)/sizeof (INT );
Int start = 0;
Int end = 0;
Int maxsum = maxsub_sum (A, size, start, end );
Cout <maxsum <"<start <" "<End <Endl;

Return 0;


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