main函数：
#include "maxsubarray.h"
#include <iostream>
using namespace std;
using namespace maxsubarray;
int main () {
    int num[6] = {1, 2 ,4, -1, 1, -1};
    Array *a = max_sub_array(num, 0, 5);
    cout<<a->left<<" ";
    cout<<a->right<<" ";
    cout<<a->sum<<endl;
    return 0;
}

头文件：
#ifndef MAX_SUB_ARRAY_H
#define MAX_SUB_ARRAY_H
namespace maxsubarray {
struct Array
{
    /* data */
    int left;
    int right;
    int sum;
};
Array* max_sub_array(int* array, int left, int right);
Array* max_crossing_sub_array(int* array, int left, int right, int mid);
}
#endif

源文件：
#include "maxsubarray.h"
using namespace maxsubarray;
Array* max_sub_array(int* array, int left, int right) {
    if (left == right) {
         Array *a = new Array;
         a->left = left;
         a->right = right;
         a->sum = array[left];
         return a;
    }
    int mid = (right - left) / 2 + left;
    Array *max_left = max_sub_array(array, left, mid);
    Array *max_right = max_sub_array(array, mid+1, right);
    Array *max_crossing = max_crossing_sub_array(array, left, right, mid);
    if (max_left->sum > max_right->sum)
        if (max_left->sum > max_crossing->sum)
            return max_left;
        else
            return max_crossing;
    else
        if (max_right->sum > max_crossing->sum)
            return max_right;
        else
            return max_crossing;
}
Array* max_crossing_sub_array(const int* array, int left, int right, int mid) {
    int max_sum_left = array[mid];
    int max_sum_right = array[mid];
    int sum = array[mid];
    int max_left = mid -1;
    int max_right = mid + 1;
    int i;
    //find the max_left
    for (i = mid-1; i >= left; i--) {
        sum += array[i];
        if (sum > max_sum_left) {
            max_sum_left = sum;
            max_left = i;
        }
    }
    // find the max_right
    sum = array[mid];
    for (i = mid+1; i <= right; i++) {
        sum += array[i];
        if (sum > max_sum_right) {
            max_sum_right = sum;
            max_right = i;
        }
    }
    Array *a = new Array;
    a->left = max_left;
    a->right = max_right;
    a->sum = max_sum_right + max_sum_left - array[mid];
    return a;
}

在linux下用G++ 编译结果：
dp@dp-ThinkPad-Edge-E430:~/Alogrithm/MaxSubArray$ g++ -o main main.cpp maxsubarray.cpp
maxsubarray.cpp: In function ‘maxsubarray::Array* max_sub_array(int*, int, int)’:
maxsubarray.cpp:14:50: error: call of overloaded ‘max_sub_array(int*&, int&, int&)’ is ambiguous
maxsubarray.cpp:14:50: note: candidates are:
maxsubarray.cpp:4:8: note: maxsubarray::Array* max_sub_array(int*, int, int)
In file included from maxsubarray.cpp:1:0:
maxsubarray.h:14:8: note: maxsubarray::Array* maxsubarray::max_sub_array(int*, int, int)
maxsubarray.cpp:15:54: error: call of overloaded ‘max_sub_array(int*&, int, int&)’ is ambiguous
maxsubarray.cpp:15:54: note: candidates are:
maxsubarray.cpp:4:8: note: maxsubarray::Array* max_sub_array(int*, int, int)
In file included from maxsubarray.cpp:1:0:
maxsubarray.h:14:8: note: maxsubarray::Array* maxsubarray::max_sub_array(int*, int, int)
dp@dp-ThinkPad-Edge-E430:~/Alogrithm/MaxSubArray$

希望高手解答

你连namespace都不了解？
第一，
将 maxsubarray.cpp 中的 using namespace maxsubarray;
改为 namespace maxsubarray { ………… }，和 maxsubarray.h 中一样。
否则就是声明一个 maxsubarray::max_sub_array，定义一个 ::max_sub_array。

第二，
头文件中写的是 Array* max_crossing_sub_array(int* array, ……
实现文件中写的是 Array* max_crossing_sub_array(const int* array, ……

以前没怎么写过命名空间， 今天查了一下C++ Prime， 接口和实现是都要包含在命名空间里面的.
谢谢了。