Problem
Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.
Example:
Input: [-2,1,-3,4,-1,2,1,-5,4],
Output: 6
Explanation: [4,-1,2,1] has the largest sum = 6.
Follow up:
If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.
Solution
/**
* @param {number[]} nums
* @return {number}
*/
var maxSubArray = function(nums) {
var len = nums.length;
var max = Number.MIN_SAFE_INTEGER;
var before = 0;
var now = 0;
if (!len) return 0;
for (var i = 0; i < len; i++) {
now = Math.max(before + nums[i], nums[i]);
max = Math.max(now, max);
before = now;
}
return max;
};
Explain:
动态规划:
当前值 = max(前值 + 当前值, 当前值)； 最大值 = max(当前值, max)
Complexity:
- Time complexity : O(n).
- Space complexity : O(1).