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.
More practice:
If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.
1 public class Solution { 2 public int maxSubArray(int[] A) { 3 // Note: The Solution object is instantiated only once and is reused by each test case. 4 int sum = 0; 5 int max = Integer.MIN_VALUE; 6 if(A == null) return 0; 7 int len = A.length; 8 if(len == 0) return 0; 9 for(int i = 0; i < len; i ++) 10 { 11 sum += A[i]; 12 if(sum > max) max = sum; 13 if(sum < 0) sum = 0; 14 } 15 return max; 16 } 17 }
这一题做了太多次了。。。。
第三遍：
1 public class Solution { 2 public int maxSubArray(int[] A) { 3 if(A == null || A.length == 0) return 0; 4 int pre = 0, sum = 0, max = Integer.MIN_VALUE; 5 while(pre < A.length){ 6 if(sum >= 0){ 7 sum += A[pre ++]; 8 max = max > sum ? max : sum; 9 }else 10 sum = 0; 11 } 12 return max; 13 } 14 }