2016 Update

Task/Chinese-remainder-theorem/Java/chinese-remainder-theorem.java

@@ -0,0 +1,46 @@
+import static java.util.Arrays.stream;
+
+public class ChineseRemainderTheorem {
+
+    public static int chineseRemainder(int[] n, int[] a) {
+
+        int prod = stream(n).reduce(1, (i, j) -> i * j);
+
+        int p, sm = 0;
+        for (int i = 0; i < n.length; i++) {
+            p = prod / n[i];
+            sm += a[i] * mulInv(p, n[i]) * p;
+        }
+        return sm % prod;
+    }
+
+    private static int mulInv(int a, int b) {
+        int b0 = b;
+        int x0 = 0;
+        int x1 = 1;
+
+        if (b == 1)
+            return 1;
+
+        while (a > 1) {
+            int q = a / b;
+            int amb = a % b;
+            a = b;
+            b = amb;
+            int xqx = x1 - q * x0;
+            x1 = x0;
+            x0 = xqx;
+        }
+
+        if (x1 < 0)
+            x1 += b0;
+
+        return x1;
+    }
+
+    public static void main(String[] args) {
+        int[] n = {3, 5, 7};
+        int[] a = {2, 3, 2};
+        System.out.println(chineseRemainder(n, a));
+    }
+}