leetCode-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.

普通版:

class Solution {
    public int maxSubArray(int[] nums) {
        int sum = 0;
        int max = Integer.MIN_VALUE;
        int len = nums.length;
        for(int i = 0;i < len;i++){
            if(sum < 0){
                sum = nums[i];
            }else{
                sum += nums[i];
            }
            if(sum > max){
                max = sum;
            }
        }
        return max;
    }
}

改进版(Math.max()函数的用法很巧妙):

class Solution {

    public int maxSubArray(int[] nums) {
        int max = nums[0];
        int sum = nums[0];

        for (int i = 1; i < nums.length; i++) {
            sum = Math.max(sum + nums[i], nums[i]);
            max = Math.max(sum, max);
        }
        return max;
    }

}