*[codility]MaxDoubleSliceSum

https://codility.com/demo/take-sample-test/max_double_slice_sum

两个最大子段和相拼接，从前和从后都扫一遍。注意其中一段可以为0。还有最后和最前面一个不可能取到~

#include <vector>

using namespace std;

int solution(vector<int> &A) {
    vector<int> maxEnd;
    maxEnd.resize(A.size());
    maxEnd[0] = 0;
    for (int i = 1; i < A.size(); i++) {
        maxEnd[i] = max(0, maxEnd[i - 1] + A[i]);
    }
    vector<int> maxBegin;
    maxBegin.resize(A.size());
    maxBegin[A.size() - 1] = 0;
    for (int i = A.size() - 2; i >= 0; i--) {
        maxBegin[i] = max(0, maxBegin[i + 1] + A[i]);
    }
    int result = maxEnd[0] + maxBegin[2];
    for (int i = 0; i + 2 < A.size(); i++) {
        int current = maxEnd[i] + maxBegin[i + 2];
        result = max(result, current);
    }
    return result;
}