Colidity-- MaxDoubleSliceSum

左右两次遍历，记录以当前元素结尾的左边最大字串和以及右边最大字串和，最后遍历，相加

 1 // you can also use includes, for example:
 2 // #include <algorithm>
 3 #include <vector>
 4 #include <algorithm>
 5 int solution(vector<int> &A) {
 6     // write your code in C++98
 7     if(A.size()==3) {
 8         return 0;
 9     }
10     int len = A.size();
11     A[0]=0;
12     A[len-1]=0;
13     vector<int> leftVec(A);
14     vector<int> rightVec(A);
15     
16     for(int i=1;i<len-1;i++) {
17         leftVec[i] = max(leftVec[i],leftVec[i]+leftVec[i-1]);
18         rightVec[len-1-i] = max(rightVec[len-1-i],rightVec[len-1-i]+rightVec[len-i]);
19     }
20     int res = A[1];
21     for(int i=1;i<len-1;i++) {
22         int tmp = leftVec[i]+rightVec[i]-A[i]*2;
23         if(tmp>res) {
24             res = tmp;
25         }
26     }
27     return res;
28 }