MATH, ARRAYS, WRAPPERS

Arrays.binarySearch() and Arrays.compare()

Arrays.binarySearch() - Requires sorted array:

Positive index if element found
Negative value if not found: -(insertion point) - 1

int[] sorted = {10, 20, 30, 40, 50};

// Element found:
int found = Arrays.binarySearch(sorted, 30);    // Returns 2
System.out.println("Found at index: " + found);

// Element not found:
int notFound = Arrays.binarySearch(sorted, 25); // Returns -3
int insertionPoint = -notFound - 1;             // -(-3) - 1 = 2
System.out.println("Would insert at index: " + insertionPoint);

Arrays.compare() vs Arrays.mismatch():

int[] a = {1, 2, 3, 4};
int[] b = {1, 2, 3, 4};
int[] c = {1, 2, 5, 4};

// Arrays.compare() - lexicographic comparison:
System.out.println(Arrays.compare(a, b));   // 0 (equal)
System.out.println(Arrays.compare(a, c));   // -2 (3 < 5, so negative)

// Arrays.mismatch() - find difference location:
System.out.println(Arrays.mismatch(a, b));  // -1 (no mismatch)
System.out.println(Arrays.mismatch(a, c));  // 2 (differ at index 2)

💡 Learning Tips:

binarySearch: “Negative means missing” - use -(result) - 1 for insertion point
compare() tells you “who wins”, mismatch() tells you “where they differ”