1.题目要求
问题: 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。
2.编写代码
代码托管所地址:
最大子段和
#include<stdio.h>
#include<stdlib.h>
int maxsub(int a[], int n);
int main()
{
int a[1000], n=0, i, m;
scanf("%d", &n);
for (i = 0; i < n; i++)
{
scanf("%d", &a[i]);
}
m = maxsub(a, n);
if (m == -1)
printf("输入错误,请检查后重新输入");
else
printf("最大字段和为%d", m);
printf("\n");
system("pause");
return 0;
}
int maxsub(int a[], int n)
{
int i = 0, Sum=0, Max=0;
if (n == 0)
Max = 0;
else if (n < 0)
Max = -1;
else if(n>0)
{
for (i = 0; i < n; i++)
{
Sum = Sum + a[i];
if (Sum > Max)
Max = Sum;
if (Sum <= 0)
Sum = 0;
}
}
return Max;
}
![](https://img2018.cnblogs.com/blog/1649100/201904/1649100-20190417100654933-662757382.png)
![](https://img2018.cnblogs.com/blog/1649100/201904/1649100-20190417100831775-1349484368.png)
3.进行单元测试
```
namespace UnitTest1
{
TEST_CLASS(UnitTest1)
{
public:
TEST_METHOD(TestMethod1)
{
int a[6] = { -2,11,-4,13,-5,-2 };
int m = 0;
m = maxsub(a, 6);
Assert::AreEqual(m, 20);
}
TEST_METHOD(TestMethod2)
{
int a[] = { 0 };
int m = 0;
m = maxsub(a, 0);
Assert::AreEqual(m, 0);
}
TEST_METHOD(TestMethod3)
{
int a[6] = {-2,-11,-4,-13,-5,-2};
int m = 0;
m = maxsub(a, 6);
Assert::AreEqual(m, 0);
}
TEST_METHOD(TestMethod4)
{
int a[6] = { -2,11,-4,13,-5,-2 };
int m = 0;
m = maxsub(a, -2);
Assert::AreEqual(m, -1);
}
};
}
<table><tr><td bgcolor=orange><font size=5 face="黑体">3.3测试样例说明</font></td></tr></table>
<table>
<thead>
<tr>
<td>测试样例</td>
<td>测试结果</td>
<td>说明</td>
</tr>
</thead>
<tbody>
<tr>
<td>n=6,a[6]={-2,11,-4,13,-5,-2}</td>
<td>20</td>
<td>正常情况最大子段和为20</td>
</tr>
<tr>
<td>n=0,a[n]={0}</td>
<td>0</td>
<td>数组中都是负数,所以为0</td>
</tr>
<tr>
<td>n=6,a[6]={-2,-11,-4,-13,-5,-2}</td>
<td>0</td>
<td>数组为空,所以为0</td>
</tr>
<tr>
<td>n=-2,a[6]={11,-4,13,-5,-2} </td>
<td>-1</td>
<td>-1表示用户输入错误,提示重新输入</td>
</tr>
</tbody>
</table>
<table><tr><td bgcolor=orange><font size=5 face="黑体">3.4测试成功</font></td></tr></table>
![](https://img2018.cnblogs.com/blog/1649100/201904/1649100-20190417101355722-1232682936.png)
   本次作业要求是求最大子段和同时进行测试,我采用的是判断条件覆盖,通过测试n是否大于零,用户的输入是否正确,以及当输入的数组的值都是负数时,该如何判断,通过这次作业,我对测试的思想以及测试工具都有了更深一步的掌握。