【leetcode】Array—— Maximum Subarray（53）

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题目：

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.

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.

思路 O(n)：要求线性复杂度，所以首先想到DP。在遍历数组的过程中，记录endWith A[i]的字串中最大的和endWithAiMax，取最大即为最终结果。

endWithAiMax初始为A[0]，i：1->A.length-1 ，如果endWithAiMax>0 , 则endWithAiMax+=A[i] ；反之，直接更新endWithAiMax=A[i]

代码：

public int maxSubArray(int[] A) {//int maxSoFar=A[0], maxEndingHere=A[0];//for (int i=1;i<A.length;++i){//maxEndingHere= Math.max(maxEndingHere+A[i],A[i]);//maxSoFar=Math.max(maxSoFar, maxEndingHere); //}//return maxSoFar;int max=A[0];int maxEndWith=A[0];for(int i=1;i<A.length;i++){if(maxEndWith<0){maxEndWith=A[i];}else{maxEndWith+=A[i];}max=Math.max(maxEndWith, max);}return max;}

思路 divide and conquer approach：
还是看看leetcode大神是怎么解决的吧：https://leetcode.com/discuss/694/how-solve-maximum-subarray-using-divide-and-conquer-approach

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