53.maximum-subarray.java

/*
 * @lc app=leetcode id=53 lang=java
 *
 * [53] Maximum Subarray
 *
 * https://leetcode.com/problems/maximum-subarray/description/
 *
 * algorithms
 * Easy (42.83%)
 * Total Accepted:    486.1K
 * Total Submissions: 1.1M
 * Testcase Example:  '[-2,1,-3,4,-1,2,1,-5,4]'
 *
 * 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.
 *
 */
class Solution {
  public int maxSubArray(int[] nums) {
    int n = nums.length;
    int[] dp = new int[n];
    dp[0] = nums[0];
    int max = dp[0];

    for (int i = 1; i < n; i++) {
      dp[i] = nums[i] + ((dp[i-1] > 0) ? dp[i-1] : 0);
      if (dp[i] > max) {
        max = dp[i];
      }
    }

    return max;
  }
}