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BentleyBsearch.java
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BentleyBsearch.java
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package com.epi;
import java.util.ArrayList;
import java.util.Arrays;
public class BentleyBsearch {
// @include
public static int bsearch(int t, ArrayList<Integer> A) {
int L = 0, U = A.size() - 1;
while (L <= U) {
int M = (L + U) / 2;
if (A.get(M) < t) {
L = M + 1;
} else if (A.get(M) == t) {
return M;
} else {
U = M - 1;
}
}
return -1;
}
// @exclude
private static void simpleTest() {
ArrayList<Integer> A = new ArrayList<>(Arrays.asList(1, 2, 3));
assert(0 == bsearch(1, A));
assert(1 == bsearch(2, A));
assert(2 == bsearch(3, A));
A = new ArrayList<Integer>(Arrays.asList(2, 2, 2));
assert(0 <= bsearch(2, A) && bsearch(2, A) <= 2);
assert(-1 == bsearch(3, A));
assert(-1 == bsearch(0, A));
}
public static void main(String[] args) {
simpleTest();
ArrayList<Integer> A = new ArrayList<>();
A.add(1);
A.add(2);
A.add(2);
A.add(2);
A.add(2);
A.add(3);
A.add(3);
A.add(3);
A.add(5);
A.add(6);
A.add(10);
A.add(100);
assert(0 == bsearch(1, A));
assert(1 <= bsearch(2, A) && bsearch(2, A) <= 4);
assert(5 <= bsearch(3, A));
assert(-1 == bsearch(4, A));
}
}