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 .

题意:就是求最大字数组和。

思路:

DP问题,O(n)内可破

对于位置arr[0]~arr[i],最大字数组和

arr[0] i==0

maxSum[i]=

max{ maxSum[i-1]+ arr[i] , arr[i] } 0<i<arr.length

具体来说该题没必要采用maxSum数组,用一个变量记住最大字数组和即可。

Java代码如下:

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

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