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.
Solution
dp
Complexity
时间复杂度 O(n),空间复杂度 O(1)
Code
public class Solution {
public int maxSubArray_1(int[] A) {
if (A.length == 0) return 0;
int minVal = Math.min(A[0],0), res = A[0], sum = A[0];
for (int i = 1; i < A.length; ++i) {
sum += A[i];
res = Math.max(res, sum - minVal);
minVal = Math.min(minVal, sum);
}
return res;
}
public int maxSubArray_2(int[] A) {
if (A.length == 0) return 0;
int dp = A[0], res = A[0];
for (int i = 1; i < A.length; ++i) {
dp = Math.max(A[i], dp + A[i]);
res = Math.max(res, dp);
}
return res;
}
}