Merge pull request #10 from Subham1999/back_tracking

Back tracking

Author: Subham1999

.idea/workspace.xml

@@ -0,0 +1,67 @@
+package com.thealgorithm.array;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @author: Subham Santra
+ */
+public class FindTwonNonOverlappingSubArrays {
+  public int minSumOfLengths(int[] arr, int target) {
+    int n = arr.length;
+    int INF = 1000_000;
+    int[] prefix = new int[n];
+    int[] suffix = new int[n];
+
+    Map<Integer, Integer> map = new HashMap<>();
+
+    int sum = 0;
+    map.put(0, -1);
+    for (int i = 0; i < n; ++i) {
+      int boundary = map.getOrDefault(sum - target, -2);
+      if (boundary != -2) {
+        prefix[i] = i - boundary - 1;
+      } else {
+        prefix[i] = (i == 0 ? INF : prefix[i - 1]);
+      }
+      sum += arr[i];
+      map.put(sum, i);
+    }
+
+    map.clear();
+    map.put(0, n);
+    sum = 0;
+
+    for (int i = n - 1; i >= 0; --i) {
+      sum += arr[i];
+      int boundary = map.getOrDefault(sum - target, -2);
+      if (boundary != -2) {
+        suffix[i] = boundary - i;
+      } else {
+        suffix[i] = (i == (n - 1) ? INF : suffix[i + 1]);
+      }
+      map.put(sum, i);
+    }
+
+//    System.out.println(Arrays.toString(prefix));
+//    System.out.println(Arrays.toString(suffix));
+
+    for (int i = 1; i < n; ++i) prefix[i] = Math.min(prefix[i - 1], prefix[i]);
+    for (int i = n - 2; i >= 0; --i) suffix[i] = Math.min(suffix[i + 1], suffix[i]);
+
+    int ans = INF;
+    for (int i = 0; i < n; ++i) {
+      ans = Math.min(ans, prefix[i] + suffix[i]);
+    }
+    return ans == INF ? -1 : ans;
+  }
+
+  public static void main(String[] args) {
+
+    System.out.println(
+        new FindTwonNonOverlappingSubArrays().minSumOfLengths(new int[] {1, 1, 2, 2, 2, 4, 3}, 3));
+
+    System.out.println(
+        new FindTwonNonOverlappingSubArrays().minSumOfLengths(new int[] {4, 3, 2, 6, 2, 3, 4}, 6));
+  }
+}