第30题——连续子数组的最大和

题目：

HZ偶尔会拿些专业问题来忽悠那些非计算机专业的同学。今天测试组开完会后,他又发话了:在古老的一维模式识别中,常常需要计算连续子向量的最大和,当向量全为正数的时候,问题很好解决。但是,如果向量中包含负数,是否应该包含某个负数,并期望旁边的正数会弥补它呢？例如:{6,-3,-2,7,-15,1,2,2},连续子向量的最大和为8(从第0个开始,到第3个为止)。给一个数组，返回它的最大连续子序列的和，你会不会被他忽悠住？(子向量的长度至少是1)

思路：

动态规划

Java

package nowcoder;

public class S30_FindGreatestSumOfSubArray {
    public int FindGreatestSumOfSubArray(int[] array){
        int length = array.length;
        if (length == 0) return 0;
        int max = 0x80000000;//初始置位最小数，int是4个字节
        int sum = 0;
        for (int i=0;i<length;i++){
            if (sum <= 0)
                sum = array[i];
            else sum += array[i];
            if (sum > max)
                max = sum;
        }
        return max;
    }
    public static void main(String[] args){
        int[] array = {1,-2,3,10,-4,7,2,-5};
        S30_FindGreatestSumOfSubArray s30 = new S30_FindGreatestSumOfSubArray();
        System.out.println(s30.FindGreatestSumOfSubArray(array));
    }
}

Python

class FindGreatestSumOfSubArray:
    def FindGreatestSumOfSubArray(self,array):
        max = 0
        temp = 0
        for i in range(len(array)):
            if temp <= 0:
                temp = array[i]
            else:
                temp += array[i]
            if temp > max:
                max = temp
        return max
if __name__ == '__main__':
    test = FindGreatestSumOfSubArray()
    array = [1,-2,3,10,-4,7,2,-5]
    print(test.FindGreatestSumOfSubArray(array))