[leetcode]53. Maximum Subarray

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

.

经典的动态规划问题。要求找出最大和的子串。定义两个变量res和sum，ress 是最终要返回的结果。每遍历一个数字num，比较sum + num和num中的较大值存入sum，然后再把res和sum中的较大值存入res，以此类推直到遍历完整个数组，。时间复杂度O(n)

public class Solution {
public int maxSubArray(int[] nums) {
if(nums==null || nums.length==0)
return 0;
int res = nums[0];
int sum = nums[0];
for(int i=1;i<nums.length;i++)
{
sum = Math.max(nums[i],sum+nums[i]);
res = Math.max(sum,res);
}
return res;
}
}