摘要：
Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2 阅读全文
摘要：
Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. Example: Note: 前缀和的应用，很简单。 阅读全文