LeetCode 30. Substring with Concatenation of All Words
Because all the words are the same length, we can use hash map to check for substring from index i to index i +word length * words number.
Because all the words are the same length, we can use hash map to check for substring from index i to index i +word length * words number.
We can calculate the water amount by columns. For position i, the water it can contains is based on the left max height column and the right max height columns.
This problem can be see as finding peak and valley. And we need to start checking the peak in order to remove the redundant count.