leetcode刷题（31）——53. 最大子序和

class Solution {
    public int maxSubArray(int[] nums) {
       if(nums.length==0){
            return 0;
        }
        int[] maxSum = new int[nums.length];
        int ans = nums[0];
        maxSum[0] = nums[0];
        for(int i=1;i<nums.length;i++){
            if(nums[i]>=0){
                maxSum[i]=maxSum[i-1]>=0?maxSum[i-1]+nums[i]:nums[i];
            }else {
                maxSum[i]=Math.max(nums[i],maxSum[i-1]+nums[i]);
            }
            ans = Math.max(ans,maxSum[i]);
        }
        return ans;
    }
}

class Solution {
    public int maxSubArray(int[] nums) {
        int ans = nums[0];
        int sum = 0;
        for(int num: nums) {
            if(sum > 0) {
                sum += num;
            } else {
                sum = num;
            }
            ans = Math.max(ans, sum);
        }
        return ans;
    }
}

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