最大子数组

题目原型：

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.

For example, given the array [−2,1,−3,4,−1,2,1,−5,4],
the contiguous subarray [4,−1,2,1] has the largest sum = 6.

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More practice:

If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.

基本思路：

令数组为A，从前往后累加得tmp，sum为最大的累加和。

1、如果A[i]>A[i]+tmp,表示，加了还不如不加，那么初始化tmp，令tmp=A[i]。若tmp>sum，则更新sum 。

2、否则，累加tmp，同时注意更新sum。

public int maxSubArray(int[] A){if(A.length==0||A==null)return 0;int sum = A[0];int tmp = A[0];for(int i = 1;i<A.length;i++){    if(A[i]>tmp+A[i]){    tmp = A[i];}else{tmp+=A[i];}if(sum<tmp)sum = tmp;}return sum;}