mirror of
https://github.com/halfrost/LeetCode-Go.git
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56 lines
1.1 KiB
Go
56 lines
1.1 KiB
Go
package leetcode
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import (
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"github.com/halfrost/LeetCode-Go/template"
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)
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//解法一 线段树，sumRange 时间复杂度 O(1)
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// NumArray define
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type NumArray struct {
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st *template.SegmentTree
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}
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// Constructor303 define
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func Constructor303(nums []int) NumArray {
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st := template.SegmentTree{}
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st.Init(nums, func(i, j int) int {
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return i + j
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})
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return NumArray{st: &st}
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}
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// SumRange define
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func (ma *NumArray) SumRange(i int, j int) int {
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return ma.st.Query(i, j)
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}
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//解法二 prefixSum，sumRange 时间复杂度 O(1)
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// // NumArray define
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// type NumArray struct {
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// prefixSum []int
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// }
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// // Constructor303 define
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// func Constructor303(nums []int) NumArray {
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// for i := 1; i < len(nums); i++ {
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// nums[i] += nums[i-1]
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// }
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// return NumArray{prefixSum: nums}
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// }
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// // SumRange define
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// func (this *NumArray) SumRange(i int, j int) int {
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// if i > 0 {
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// return this.prefixSum[j] - this.prefixSum[i-1]
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// }
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// return this.prefixSum[j]
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// }
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/**
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* Your NumArray object will be instantiated and called as such:
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* obj := Constructor(nums);
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* param_1 := obj.SumRange(i,j);
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*/
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