JZ-C-31

剑指offer第三十一题：连续子数组的最大和
 1 //============================================================================
 2 // Name        : JZ-C-31.cpp
 3 // Author      : Laughing_Lz
 4 // Version     :
 5 // Copyright   : All Right Reserved
 6 // Description : 连续子数组的最大和
 7 //============================================================================
 8 
 9 #include <iostream>
10 #include <stdio.h>
11 using namespace std;
12 
13 bool g_InvalidInput = false;
14 
15 int FindGreatestSumOfSubArray(int *pData, int nLength) {
16     if ((pData == NULL) || (nLength <= 0)) {
17         g_InvalidInput = true;
18         return 0;
19     }
20 
21     g_InvalidInput = false;
22 
23     int nCurSum = 0;
24     int nGreatestSum = 0x80000000;//最小的整数。int 4个字节，最小数：-2^31:0x80000000，最大数：2^32-1:0x7fffffff。（均为补码）
25     for (int i = 0; i < nLength; ++i) {
26         if (nCurSum <= 0)
27             nCurSum = pData[i];
28         else
29             nCurSum += pData[i];
30 
31         if (nCurSum > nGreatestSum)
32             nGreatestSum = nCurSum;
33     }
34 
35     return nGreatestSum;
36 }
37 
38 // ====================测试代码====================
39 void Test(char* testName, int* pData, int nLength, int expected,
40         bool expectedFlag) {
41     if (testName != NULL)
42         printf("%s begins: 
", testName);
43 
44     int result = FindGreatestSumOfSubArray(pData, nLength);
45     if (result == expected && expectedFlag == g_InvalidInput)
46         printf("Passed.
");
47     else
48         printf("Failed.
");
49 }
50 
51 // 1, -2, 3, 10, -4, 7, 2, -5
52 void Test1() {
53     int data[] = { 1, -2, 3, 10, -4, 7, 2, -5 };
54     Test("Test1", data, sizeof(data) / sizeof(int), 18, false);
55 }
56 
57 // 所有数字都是负数
58 // -2, -8, -1, -5, -9
59 void Test2() {
60     int data[] = { -2, -8, -1, -5, -9 };
61     Test("Test2", data, sizeof(data) / sizeof(int), -1, false);
62 }
63 
64 // 所有数字都是正数
65 // 2, 8, 1, 5, 9
66 void Test3() {
67     int data[] = { 2, 8, 1, 5, 9 };
68     Test("Test3", data, sizeof(data) / sizeof(int), 25, false);
69 }
70 
71 // 无效输入
72 void Test4() {
73     Test("Test4", NULL, 0, 0, true);
74 }
75 
76 int main(int argc, char** argv) {
77     Test1();
78     Test2();
79     Test3();
80     Test4();
81 
82     return 0;
83 }