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@@ -0,0 +1,46 @@
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+type NumArray struct {
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+ seg []int
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+ l int
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+}
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+
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+func Constructor(nums []int) (numArr NumArray) { // Segment tree, O(n) construction, O(logn) update, O(logn) sum range
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+ numArr.l = len(nums)
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+ numArr.seg = make([]int, 2*numArr.l)
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+ copy(numArr.seg[numArr.l:], nums)
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+ for i := numArr.l - 1; 0 < i; i-- {
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+ numArr.seg[i] = numArr.seg[2*i] + numArr.seg[2*i+1]
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+ }
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+ return
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+}
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+
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+func (this *NumArray) Update(i int, val int) {
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+ i += this.l
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+ this.seg[i] = val
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+ for i = i / 2; 0 < i; i /= 2 {
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+ this.seg[i] = this.seg[2*i] + this.seg[2*i+1]
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+ }
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+}
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+
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+func (this *NumArray) SumRange(i int, j int) (sum int) {
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+ for i, j = i+this.l, j+this.l; i < j; i, j = i/2, j/2 {
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+ if i%2 == 1 {
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+ sum += this.seg[i]
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+ i++
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+ }
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+ if j%2 == 0 {
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+ sum += this.seg[j]
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+ j--
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+ }
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+ }
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+ if i == j {
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+ sum += this.seg[i]
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+ }
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+ return
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+}
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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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+ * obj.Update(i,val);
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+ * param_2 := obj.SumRange(i,j);
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+ */
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