欢迎进入Java社区论坛，与200万技术人员互动交流 >>进入
import java.util.Random;
public final class MaxSumTest
{
static private int seqStart = 0;
static private int seqEnd = -1;
/**
* Cubic maximum contiguous subsequence sum algorithm.
* seqStart and seqEnd represent the actual best sequence.
*/
public static int maxSubSum1( int [ ] a )
{
int maxSum = 0;
for( int i = 0; i < a.length; i++ )
for( int j = i; j < a.length; j++ )
{
int thisSum = 0;
for( int k = i; k <= j; k++ )
thisSum += a[ k ];
if( thisSum > maxSum )
{
maxSum = thisSum;
seqStart = i;
seqEnd = j;
}
}
return maxSum;
}
/**
* Quadratic maximum contiguous subsequence sum algorithm.
* seqStart and seqEnd represent the actual best sequence.
*/
public static int maxSubSum2( int [ ] a )
{
int maxSum = 0;
for( int i = 0; i < a.length; i++ )
{
int thisSum = 0;
for( int j = i; j < a.length; j++ )
{
thisSum += a[ j ];
if( thisSum > maxSum )
{
maxSum = thisSum;
seqStart = i;
seqEnd = j;
}
}
}
return maxSum;
}
/**
* Linear-time maximum contiguous subsequence sum algorithm.
* seqStart and seqEnd represent the actual best sequence.
*/
public static int maxSubSum3( int [ ] a )
{
int maxSum = 0;
int thisSum = 0;
for( int i = 0, j = 0; j < a.length; j++ )
{
thisSum += a[ j ];
if( thisSum > maxSum )
{
maxSum = thisSum;
seqStart = i;
seqEnd = j;
}
else if( thisSum < 0 )
{
i = j + 1;
thisSum = 0;
}
}
return maxSum;
}
/**
* Recursive maximum contiguous subsequence sum algorithm.
* Finds maximum sum in subarray spanning a[left..right].
* Does not attempt to maintain actual best sequence.
*/
private static int maxSumRec( int [ ] a, int left, int right )
{
int maxLeftBorderSum = 0, maxRightBorderSum = 0;
int leftBorderSum = 0, rightBorderSum = 0;
int center = ( left + right ) / 2;
if( left == right ) // Base case
return a[ left ] > 0 ? a[ left ] : 0;
int maxLeftSum = maxSumRec( a, left, center );
int maxRightSum = maxSumRec( a, center + 1, right );
for( int i = center; i >= left; i? )
{
leftBorderSum += a[ i ];
if( leftBorderSum > maxLeftBorderSum )
maxLeftBorderSum = leftBorderSum;
}
for( int i = center + 1; i <= right; i++ )
{
rightBorderSum += a[ i ];
if( rightBorderSum > maxRightBorderSum )
maxRightBorderSum = rightBorderSum;
}
return max3( maxLeftSum, maxRightSum,
maxLeftBorderSum + maxRightBorderSum );
}
[1][2]
怪天怪地，我都不会怪你，你有选择幸福的权利…
