[LeetCode] Trapping Rain Water 栈

 1 #include <iostream>
 2 #include <stack>
 3 using namespace std;
 4 
 5 class Solution {
 6 public:
 7     int trap(int A[], int n) {
 8         if(n<3) return 0;
 9         int curIdx = 0;
10 
11         stack<int> stk;
12 
13         int retSum = 0;
14         for(;curIdx<n;curIdx++){
15             if(stk.empty()){
16                 stk.push(curIdx);
17                 continue;
18             }
19             int stkTop = stk.top();
20             if(A[stkTop]>=A[curIdx]){
21                 stk.push(curIdx);
22                 continue;
23             }
24             while(!stk.empty()){
25                 int dit = stkTop;
26                 stk.pop();
27                 if(stk.empty()) break;
28                 stkTop =stk.top();
29                 retSum += (min(A[stkTop],A[curIdx])-A[dit])*(curIdx-stkTop - 1);
30                 if(A[stkTop]>A[curIdx]) break;
31             }
32             stk.push(curIdx);
33         }
34         return retSum;
35     }
36 };
37 
38 int main()
39 {
40     int A[]= {0,1,0,2,1,0,1,3,2,1,2,1};
41     Solution sol;
42     cout<<sol.trap(A,sizeof(A)/sizeof(int))<<endl;
43     return 0;
44 }