FindSubarrays added

Author: coding-parrot

src/main/java/main/java/videos/FindSubarrays.java

@@ -0,0 +1,72 @@
+package videos;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class FindSubarrays {
+ public static void main(String[] args) {
+ }
+
+ public int numberOfSubarrays(final String a, final int p, final int q) {
+// System.out.println("MY TRY");
+ final int length = a.length();
+ final int[] sum = new int[length];
+ getSums(a, length, sum);
+ final int L = p + q;
+ //count of possible combinations (diff, difference)
+ final Map<Integer, Integer>[] count = new HashMap[L];
+ int difference = 0;
+ for (int i = 0; i < L; i++) {
+ count[i] = new HashMap<>();
+ }
+ for (int i = 0; i < a.length(); i++) {//f[0]*q-f[1]*p = 0
+ difference = difference + (a.charAt(i) == '0' ? p : -q);
+ final int offset = i % L;
+ count[offset].put(difference, count[offset].getOrDefault(difference, 0) + 1);
+ }
+// System.out.println("SUMS: " + Arrays.toString(sum));
+// System.out.println("COUNTS: " + count);
+ int total = 0;
+ for (int i = 0; i < L; i++) {
+ for (Map.Entry<Integer, Integer> entry : count[i].entrySet()) {
+ int v = entry.getValue();
+ if (entry.getKey() == 0 && i == L - 1) {
+ v++;
+ }
+ total += (v * (v - 1)) / 2;
+// System.out.println("TOTAL: " + total + " " + i + " " + v);
+ }
+ }
+ return total;
+ }
+
+ public int bruteForce(final String a, final int p, final int q) {
+ final int length = a.length();
+ final int[] sum = new int[length];
+ getSums(a, length, sum);
+ final int L = p + q;
+ int count = 0;
+ for (int i = 0; i < length; i++) {
+ for (int j = 1; i - j * L >= -1; j++) {
+ final int end = i - j * L;
+ if (end == -1) {
+ if (sum[i] == p * j) {
+// System.out.println(0 + " " + i + " " + 0);
+ count++;
+ }
+ } else if (sum[i] - sum[end] == p * j) {
+// System.out.println(((end + 1) % L) + " " + i + " " + (end + 1));
+ count++;
+ }
+ }
+ }
+ return count;
+ }
+
+ private void getSums(String a, int length, int[] sum) {
+ sum[0] = a.charAt(0) - '0';
+ for (int i = 1; i < length; i++) {
+ sum[i] = sum[i - 1] + a.charAt(i) - '0';
+ }
+ }
+}