求數組最大子序列的和

題目：給出數組{4,-3,5,-2,-1,2,6,-2}，求子序列的最大和。

分別用一下兩種方法解決。

#include <stdio.h>
// 方法1：  分治法
//時間複雜度 O(NlogN)
int max3(int num1 , int num2 , int num3){
    int max = num1;
    if(max<num2)max= num2;
    if(max<num3)max=num3;
    return max;
}
int  maxSubSum(int array[],int start, int end){
    int maxLeftSum , maxRightSum;
    int maxLeftBorderSum,maxRightBorderSum;
    int leftBorderSum,rightBorderSum;
    int middle,i;

    if(start == end){
        if(array[start] >0)
            return array[start];
        else
            return 0;
    }



    middle = (start+ end)/2;
    //遞歸求解左半部分最大子序列和
    maxLeftSum = maxSubSum(array, start, middle);
    //遞歸求解右半部分最大子序列和
    maxRightSum = maxSubSum(array, middle+1, end);

    //求解中間部分的最大子序列和
    leftBorderSum=0,maxLeftBorderSum=0;
    for(i = middle;i>=start;i--){
        leftBorderSum+=array[i];
        if(leftBorderSum>maxLeftBorderSum)
            maxLeftBorderSum = leftBorderSum;
    }
    rightBorderSum =0,maxRightBorderSum=0;
    for (i=middle+1; i<=end; i++) {
        rightBorderSum+=array[i];
        if(rightBorderSum>maxRightBorderSum){
            maxRightBorderSum = rightBorderSum;
        }

    }
    return max3(maxLeftSum, maxRightSum, maxLeftBorderSum+maxRightBorderSum);

}


//方法2 時間複雜度  o(N)

int getMaxSubSum(int array[],int start,int end){
    int currentSum = 0, maxSum =0;
    for(int i = start;i <=end;i++){
        currentSum+=array[i];
        if(currentSum<0)
            currentSum= array[i];
        if(currentSum>maxSum){
            maxSum = currentSum;
        }
    }
    return maxSum;
}
int main(int argc, const char * argv[]) {
    // insert code here...
    int a[] = {4,-3,5,-2,-1,2,6,-2};
    //int max = maxSubSum(a, 0, 7);
    int max = getMaxSubSum(a, 0, 7);
    printf("%d",max);
    return 0;
}