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@@ -0,0 +1,37 @@
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+type Solution struct {
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+ sum []int
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+ l int
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+ n int
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+}
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+
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+func Constructor(w []int) (sol Solution) {
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+ n := len(w)
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+ sol.sum = make([]int, n+1)
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+ for i := range w {
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+ sol.sum[i+1] = sol.sum[i] + w[i]
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+ }
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+ sol.n, sol.l = sol.sum[n], n+1
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+ return
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+}
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+
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+func (this *Solution) PickIndex() int {
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+ idx := rand.Intn(this.n) + 1
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+ beg, end := 1, this.l-1
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+ for beg <= end {
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+ mid := beg + (end - beg)
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+ if val := this.sum[mid]; val == idx {
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+ return mid - 1
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+ } else if val < idx {
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+ beg = mid + 1
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+ } else {
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+ end = mid - 1
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+ }
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+ }
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+ return beg - 1
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+}
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+
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+/**
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+ * Your Solution object will be instantiated and called as such:
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+ * obj := Constructor(w);
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+ * param_1 := obj.PickIndex();
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+ */
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