problem0304

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Published: Jul 25, 2019 License: MIT Imports: 0 Imported by: 0

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304. Range Sum Query 2D - Immutable

题目

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, col2).

range_sum_query_2d

The above rectangle (with the red border) is defined by (row1, col1) = (2, 1) and (row2, col2) = (4, 3), which contains sum = 8.

Example:

Given matrix = [
  [3, 0, 1, 4, 2],
  [5, 6, 3, 2, 1],
  [1, 2, 0, 1, 5],
  [4, 1, 0, 1, 7],
  [1, 0, 3, 0, 5]
]

sumRegion(2, 1, 4, 3) -> 8
sumRegion(1, 1, 2, 2) -> 11
sumRegion(1, 2, 2, 4) -> 12

Note:

  1. You may assume that the matrix does not change.
  2. There are many calls to sumRegion function.
  3. You may assume that row1 ≤ row2 and col1 ≤ col2.

解题思路

见程序注释

Documentation

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type NumMatrix

type NumMatrix struct {
	// contains filtered or unexported fields
}

NumMatrix 包含了需要求和的矩阵

func Constructor

func Constructor(matrix [][]int) NumMatrix

Constructor 创建 NumMatrix

func (*NumMatrix) SumRegion

func (nm *NumMatrix) SumRegion(row1 int, col1 int, row2 int, col2 int) int

SumRegion 求和

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