求数组最大子数组和

(1).题目描述

给定n个整数（可能为负数）组成的序列a[1],a[2],a[3],…,a[n],求该序列如a[i]+a[i+1]+…+a[j]的子段和的最大值。当所给的整数均为负数时定义子段和为0，依此定义，所求的最优值为： Max{0,a[i]+a[i+1]+…+a[j]},1<=i<=j<=n
例如，当（a[1],a[2],a[3],a[4],a[5],a[6]）=(-2,11,-4,13,-5,-2)时，最大子段和为20。
-- 引用自

(2).功能函数：

//求最大子数组和    public static int maxarraysum(int[] array) {        int maxsum = 0; //最大和        int sum = 0;  //记录子串的和          for(int i = 0; i < array.length; i++) {            sum += array[i];            if(sum  > maxsum) {                maxsum = sum;               }else if(sum < 0) { //子串和为0则应丢弃，，子串和赋0值                sum = 0;                }        }        return maxsum;    }

(3).流程图

（4).单元测试

本次单元测试采用判定条件覆盖，

条件组合	程序执行路径
sum > maxsum	abfg
sum < maxsum,sum<0	acdg
sum < maxsum,sum>0	aceg

选取三组测试用例，测试用例如下

{2,4,6,2,4,8,9}

{-2,-4,-6,-2,-4,-8,-9}

{10,-2,-1,-2,-3}

测试类：

public class MaxarraysumTest {    @Test    public void testMaxarraysum() {        int[] array_1 =  {2,4,6,2,4,8,9};        int[] array_2 = {-2,-4,-6,-2,-4,-8,-9};        int[] array_3 = {10,-2,-1,-2,-3};        assertEquals(35, new MaxSubArray().maxarraysum(array_1));        assertEquals(0, new MaxSubArray().maxarraysum(array_2));        assertEquals(10, new MaxSubArray().maxarraysum(array_3));    }}