最大子列和 O(nlog n) O(n)

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public static int (int array[], int n) {
int this_sum,max_sum;
this_sum=0;
max_sum=0;
for (int i = 0; i < n; i++) {
this_sum=0;
for (int j = i; j < n; j++) {
this_sum += array[j];
if (this_sum > max_sum) {
max_sum = this_sum;
}
}
}
return max_sum;
}

O(nlog n)

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//O(nlog(n))

public static int max_three(int a, int b, int c) {
int temp=a>b?a:b;
return temp > c ? temp : c;
}
public static int getCrossMax(int array[], int low, int mid, int hign) {
int left_sum = 0;
int right_sum = 0;
int left_max = 0;
int right_max = 0;
for (int i = mid; i >= low; i--) {
left_sum += array[i];
if (left_sum > left_max) {
left_max = left_sum;
}
}
for (int i = mid + 1; i <= hign; i++) {
right_sum += array[i];
if (right_sum > right_max) {
right_max = right_sum;
}
}
return left_max + right_max;
}

public static int getMaxSubArraySum(int array[], int low, int hign) {
if (low == hign) {
return array[low];
}

int mid=low+(hign-low)/2;
int left_sum = getMaxSubArraySum(array, low, mid);
int right_sum = getMaxSubArraySum(array, mid + 1, hign);
int cross_sum = getCrossMax(array, low, mid, hign);
return max_three(left_sum, right_sum, cross_sum);
}

O(n)

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//O(n)
public static int process_online(int array[], int n) {
int this_sum,max_sum;
this_sum=max_sum=0;

for (int i = 0; i < n; i++) {
this_sum += array[i];
if (this_sum > max_sum) {
max_sum = this_sum;
}
if (this_sum <= 0) {
this_sum = 0;
}
}
return max_sum;
}