int trap(int A[], int n) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if(n <= 2)
return 0;
vector<int> leftMax(n, 0);
vector<int> rightMax(n, 0);
leftMax[0] = A[0];
rightMax[n-1] = A[n-1];
for(int i = 1; i < n-1; i++)
{
leftMax[i] = max(leftMax[i-1], A[i]);
rightMax[n-1-i] = max(rightMax[n-1-i+1], A[n-1-i]);
}
int ret = 0;
for(int i = 1; i< n-1; i++)
{
ret += (leftMax[i] > rightMax[i]?rightMax[i]:leftMax[i])-A[i];
}
return ret;
}
int trap(vector<int>& height)
{
int len = height.size();
if (len == 0) { return 0; }
vector<int> leftMax(len, 0);
vector<int> rightMax(len, 0);
int maxL = 0;
int maxR = 0;
for (int i = 0; i < len; i++)
{
leftMax[i] = maxL;
maxL = max(maxL, height[i]);
rightMax[len - 1 - i] = maxR;
maxR = max(maxR, height[len - 1 - i]);
}
int result = 0;
for (int i = 0; i < len; i++)
{
result += max(min(leftMax[i], rightMax[i]) - height[i], 0);
}
return result;
}