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Range Sum Query - Immutable

DynamicProgramming, Go, LeetCode

Range Sum Query - Immutable

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.

For Example:

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Given nums = [-2, 0, 3, -5, 2, -1]
sumRange(0, 2) -> 1
sumRange(2, 5) -> -1
sumRange(0, 5) -> -3

Note:

  1. You may assume that the array does not change.
  2. There are many calls to sumRange function.
提示 解題應用
DynamicProgramming 物件概念

Default:

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type NumArray struct {
    
}
func Constructor(nums []int) NumArray {
    
}
func (this *NumArray) SumRange(i int, j int) int {
    
}
/**
 * Your NumArray object will be instantiated and called as such:
 * obj := Constructor(nums);
 * param_1 := obj.SumRange(i,j);
 */

解答思路:

這題沒有什麼技巧，單純測試最基本的物件概念實作，而物件的function是要算出該陣列中index範圍間的總合，基本上就是初始化時將值存入物件，最後在function去呼叫儲存在物件的陣列，用迴圈遍歷範圍值總合回傳就結束了。

程式碼解說:

首先先定義好要存在物件裡值的型別，接著當建構function被呼叫時將值帶入一個初始化的物件並回傳，最後在SumRange被呼叫時利用this來存取初始化帶入的陣列，並用迴圈遍歷範圍的index值做總合回傳

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type NumArray struct {
	Nums []int
}
func Constructor(nums []int) NumArray {
	return NumArray{nums}
}
func (this *NumArray) SumRange(i int, j int) int {
	var sum int
	for i <= j {
		sum += this.Nums[i]
		i++
	}
	return sum
}

完整程式碼:

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type NumArray struct {
	Nums []int
}
func Constructor(nums []int) NumArray {
	return NumArray{nums}
}
func (this *NumArray) SumRange(i int, j int) int {
	var sum int
	for i <= j {
		sum += this.Nums[i]
		i++
	}
	return sum
}

總結:

物件概念的基本實作。

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