Count number of matching elements in two integer arrays

Solution.java

import java.util.Arrays;

class Solution {

    public static int solve(int[] A, int[] B) {
        int i = 0;
        int j = 0;

        Arrays.sort(A);
        Arrays.sort(B);

        int matches = 0;

        while (i < A.length && j < B.length) {
            if (A[i] == B[j]) {
                matches++;
                j++;
            } else if (A[i] < B[j]) {
                i++;
            } else {
                j++;
            }
        }

        return matches;
    }

    public static void main(String[] args) {
        int[] A = {1, 3, 9, 2};
        int[] B = {1, 3, 20, 5, 2};

        System.out.println("Starting");

        // 3 should match
        System.out.println(Solution.solve(A, B));

        int[] C = {0, 6, 12, 18, 24, 30};
        int[] D = {0, 12, 24, 36, 48, 60};

        // 3 should match
        System.out.println(Solution.solve(C, D));

        int[] E = {1, 2, 3, 4, 5, 6, 7};

        // 7 should match
        System.out.println(Solution.solve(E, E));

        int[] F = {-1, -2, -3, -4, -5, -6, -7};

        // 0 should match
        System.out.println(Solution.solve(E, F));
    }
}

solution.php

<?php
function solution($A, $B) {
    $a_counts = $b_counts = array();

    foreach ($A as $a) {
        $a_counts[$a] = isset($a_counts[$a]) ? $a_counts[$a] + 1 : 1;
        $b_counts[$a] = isset($b_counts[$a]) ? $b_counts[$a] : 0;
    }

    foreach ($B as $b) {
        $a_counts[$b] = isset($a_counts[$b]) ? $a_counts[$b] : 0;
        $b_counts[$b] = isset($b_counts[$b]) ? $b_counts[$b] + 1 : 1;
    }

    $duplicates = 0;

    foreach ($a_counts as $k => $v) {
        $duplicates += min($v, $b_counts[$k]);
    }

    return $duplicates;
}

function solution2($A, $B) {
    $a_counts = array_count_values($A);
    $b_counts = array_count_values($B);
    $a_counts += array_fill_keys(array_keys($b_counts), 0);

    $duplicates = 0;

    foreach ($a_counts as $k => $v) {
        $duplicates += isset($b_counts[$k]) ? min($v, $b_counts[$k]) : 0;
    }

    return $duplicates;
}

Output:

nasatyau@DANTE [~/Dropbox/codebox/java]$ java Solution
Starting
3
3
7
0