最大子列和问题

#include<stdio.h>
int MaxSubseqSum1(int A[], int N);
int MaxSubseqSum2(int A[], int N);
int MaxSubseqSum3(int A[], int N);
int Max3(int A, int B, int C);
int DevideAndConquer(int A[], int left, int right);
int main()
{
int MaxSum;
int A[100000];
int N;
int i;
scanf("%d", &N);
for(i=0; i<N; i++)
{
scanf("%d", &A[i]);
}
MaxSum = MaxSubseqSum3(A, N);
printf("%d\n", MaxSum);
return 0;
}

int MaxSubseqSum1(int A[], int N)
{
int ThisSum, MaxSum=0;
int i, j, k;
for(i=0; i<N; i++)
{
for(j=i; j<N; j++)
{
ThisSum = 0;
for(k=i; k<=j; k++)
{
ThisSum += A[k];
}
if(ThisSum > MaxSum)
{
MaxSum = ThisSum;
}
}
}
return MaxSum;
}
int MaxSubseqSum2(int A[], int N)
{
int ThisSum, MaxSum=0;
int i, j, k;
for(i=0; i<N; i++)
{
ThisSum = 0;
for(j=i; j<N; j++)
{
ThisSum += A[j];
if(ThisSum > MaxSum)
{
MaxSum = ThisSum;
}
}
}
return MaxSum;
}
int DevideAndConquer(int A[], int left, int right)
{
if(left == right)
{
if(A[left] > 0)
{
return A[left];
}
else
{
return 0;
}
}
int MaxLeft=0, MaxRight=0, MaxLeftBorderSum=0, MaxRightBorderSum=0, LeftBorderSum=0, RightBorderSum=0;
int i=0;
int center = (left+right) / 2;
MaxLeft = DevideAndConquer(A, left, center);
MaxRight = DevideAndConquer(A, center+1, right);

for(i=center; i>=left; i--)
{
LeftBorderSum += A[i];
if(LeftBorderSum > MaxLeftBorderSum)
{
MaxLeftBorderSum = LeftBorderSum;
}
}

for(i=center+1; i<=right; i++)
{
RightBorderSum += A[i];
if(RightBorderSum > MaxRightBorderSum)
{
MaxRightBorderSum = RightBorderSum;
}
}

return Max3(MaxLeft, MaxRight, MaxLeftBorderSum+MaxRightBorderSum);
}
int MaxSubseqSum3(int A[], int N)
{
DevideAndConquer(A, 0, N-1);
}
int Max3(int A, int B, int C)
{
return A>B ? A>C?A:C : B>C?B:C;
}