JZ-C-31

剑指offer第三十一题：连续子数组的最大和

//============================================================================
// Name        : JZ-C-31.cpp
// Author      : Laughing_Lz
// Version     :
// Copyright   : All Right Reserved
// Description : 连续子数组的最大和
//============================================================================

#include <iostream>
#include <stdio.h>
using namespace std;

bool g_InvalidInput = false;

int FindGreatestSumOfSubArray(int *pData, int nLength) {
    if ((pData == NULL) || (nLength <= 0)) {
        g_InvalidInput = true;
        return 0;
    }

    g_InvalidInput = false;

    int nCurSum = 0;
    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）
    for (int i = 0; i < nLength; ++i) {
        if (nCurSum <= 0)
            nCurSum = pData[i];
        else
            nCurSum += pData[i];

        if (nCurSum > nGreatestSum)
            nGreatestSum = nCurSum;
    }

    return nGreatestSum;
}

// ====================测试代码====================
void Test(char* testName, int* pData, int nLength, int expected,
        bool expectedFlag) {
    if (testName != NULL)
        printf("%s begins: 
", testName);

    int result = FindGreatestSumOfSubArray(pData, nLength);
    if (result == expected && expectedFlag == g_InvalidInput)
        printf("Passed.
");
    else
        printf("Failed.
");
}

// 1, -2, 3, 10, -4, 7, 2, -5
void Test1() {
    int data[] = { 1, -2, 3, 10, -4, 7, 2, -5 };
    Test("Test1", data, sizeof(data) / sizeof(int), 18, false);
}

// 所有数字都是负数
// -2, -8, -1, -5, -9
void Test2() {
    int data[] = { -2, -8, -1, -5, -9 };
    Test("Test2", data, sizeof(data) / sizeof(int), -1, false);
}

// 所有数字都是正数
// 2, 8, 1, 5, 9
void Test3() {
    int data[] = { 2, 8, 1, 5, 9 };
    Test("Test3", data, sizeof(data) / sizeof(int), 25, false);
}

// 无效输入
void Test4() {
    Test("Test4", NULL, 0, 0, true);
}

int main(int argc, char** argv) {
    Test1();
    Test2();
    Test3();
    Test4();

    return 0;
}