weekly-241

Signed-off-by: ashKIK <[email protected]>

Author: px100

.gitignore

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+# Default ignored files
+/shelf/
+/.idea/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml
+# Editor-based HTTP Client requests
+/httpRequests/

weekly-241/FindingPairsWithACertainSum.java

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+import java.util.HashMap;
+import java.util.Map;
+
+// https://leetcode.com/contest/weekly-contest-241/problems/finding-pairs-with-a-certain-sum/
+
+public class FindingPairsWithACertainSum {
+
+  class FindSumPairs {
+
+    private int[] nums1;
+    private int[] nums2;
+    private Map<Integer, Integer> map;
+
+    public FindSumPairs(int[] nums1, int[] nums2) {
+      this.map = new HashMap<>();
+      this.nums1 = nums1;
+      this.nums2 = nums2;
+      for (int num2 : nums2) {
+        map.merge(num2, 1, Integer::sum);
+      }
+    }
+
+    public void add(int index, int val) {
+      map.merge(nums2[index], -1, Integer::sum);
+      nums2[index] += val;
+      map.merge(nums2[index], 1, Integer::sum);
+    }
+
+    public int count(int tot) {
+      int count = 0;
+      for (int num : nums1) {
+        count += map.getOrDefault(tot - num, 0);
+      }
+      return count;
+    }
+  }
+
+/**
+ * Your FindSumPairs object will be instantiated and called as such:
+ * FindSumPairs obj = new FindSumPairs(nums1, nums2);
+ * obj.add(index,val);
+ * int param_2 = obj.count(tot);
+ */
+}

weekly-241/MinimumNumberOfSwapsToMakeTheBinaryStringAlternating.java

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+
+// https://leetcode.com/contest/weekly-contest-241/problems/minimum-number-of-swaps-to-make-the-binary-string-alternating/
+
+public class MinimumNumberOfSwapsToMakeTheBinaryStringAlternating {
+
+  public int minSwaps(String s) {
+    int numOnes = 0;
+    int numZeros = 0;
+    int countOnes = 0;
+    int countZeros = 0;
+
+    // two patters; either 10101 or 01010
+    char one = '1';
+    char zero = '0';
+
+    for (int i = 0; i < s.length(); i++) {
+      char c = s.charAt(i);
+      if (c == '1') {
+        numOnes++;
+      }
+      if (c == '0') {
+        numZeros++;
+      }
+      if (c != one) {
+        countOnes++;
+      }
+      if (c != zero) {
+        countZeros++;
+      }
+      // alternate the 10101 or 01010 pattern
+      one = one == '1' ? '0' : '1';
+      zero = zero == '1' ? '0' : '1';
+    }
+    if (Math.abs(numOnes - numZeros) > 1) {
+      return -1;
+    }
+    // if the difference is odd, then impossible to make 10101 pattern, make 01010 instead
+    // vice versa
+    if (countOnes % 2 == 1) {
+      return countZeros / 2;
+    }
+    if (countZeros % 2 == 1) {
+      return countOnes / 2;
+    }
+    // if able to alter to both patters then return minimum
+    return Math.min(countOnes / 2, countZeros / 2);
+  }
+}

weekly-241/NumberOfWaysToRearrangeSticksWithKSticksVisible.java

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+
+// https://leetcode.com/contest/weekly-contest-241/problems/number-of-ways-to-rearrange-sticks-with-k-sticks-visible/
+
+public class NumberOfWaysToRearrangeSticksWithKSticksVisible {
+
+  private final int[][] dp = new int[1001][1001];
+  private final int MOD = 1000000007;
+
+  public int rearrangeSticks(int n, int k) {
+    if (n == k) {
+      return 1;
+    }
+    if (k == 0) {
+      return 0;
+    }
+    if (dp[n][k] == 0) {
+      dp[n][k] = (int) (((long) rearrangeSticks(n - 1, k - 1)
+          + (long) rearrangeSticks(n - 1, k) * (n - 1)) % MOD);
+    }
+    return dp[n][k];
+  }
+}

weekly-241/SumOfAllSubsetXORTotals.java

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+
+// https://leetcode.com/contest/weekly-contest-241/problems/sum-of-all-subset-xor-totals/
+
+public class SumOfAllSubsetXORTotals {
+
+  public int subsetXORSum(int[] nums) {
+    int res = 0;
+    for (int num : nums) {
+      res |= num;
+    }
+    return res * (1 << nums.length - 1);
+  }
+}