problem0304

README

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).

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

• type NumMatrix
  • func Constructor(matrix [][]int) NumMatrix
  • func (nm *NumMatrix) SumRegion(row1 int, col1 int, row2 int, col2 int) int

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