最大的子序列之和

#include<iostream>
#include "utils_common.h"

#define ARR_SIZE(a) ((sizeof(a))/sizeof((a[0])))

int cal_sum(const int arr[], int len)
{
    int sum, this_sum, i,j,k;
    sum = 0;
    for(i = 0; i < len; i++) {
        for(j = i; j < len; j++) {
            this_sum = 0;
            for(k = i; k <=j; k++) {
                this_sum += arr[k];
                if(this_sum > sum) {
                    sum = this_sum;
                }
            }
        }
    }

    return sum;
}

int cal_sum2(const int arr[], int len)
{
    int sum, this_sum, i,j;
    sum = 0;
    for(i = 0; i < len; i++) {
        this_sum = 0;
        for(j = i; j < len; j++) {
            this_sum += arr[j];
            if(this_sum > sum) {
                sum = this_sum;
            }
        }
    }

    return sum;
}

int main()
{
// int arr[] = { -10, -2, 3, -1, 6};
    int arr[] = { -10, -3, 5, -2, -1, 2, 6, -2 };
    int len = ARR_SIZE(arr);
    cout << len << endl;

    int sum;
    sum = cal_sum(arr, len);

    cout << "sum=" << sum << "\tlen=" << len << endl;
    sum = cal_sum2(arr, len);
    cout << "sum=" << sum << endl;

    sum = cal_sum3(arr, len);
    cout << "sum=" << sum << endl;
    return 0;
}