888. Fair Candy Swap.md

888. Fair Candy Swap

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leetcode-cn Daily Challenge on Feburary 1st, 2021.

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Difficulty : Easy

Related Topics : Array

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Alice and Bob have candy bars of different sizes: A[i] is the size of the i-th bar of candy that Alice has, and B[j] is the size of the j-th bar of candy that Bob has.

Since they are friends, they would like to exchange one candy bar each so that after the exchange, they both have the same total amount of candy. (The total amount of candy a person has is the sum of the sizes of candy bars they have.)

Return an integer array ans where ans[0] is the size of the candy bar that Alice must exchange, and ans[1] is the size of the candy bar that Bob must exchange.

If there are multiple answers, you may return any one of them. It is guaranteed an answer exists.

Example 1:

Input: A = [1,1], B = [2,2]
Output: [1,2]

Example 2:

Input: A = [1,2], B = [2,3]
Output: [1,2]

Example 3:

Input: A = [2], B = [1,3]
Output: [2,3]

Example 4:

Input: A = [1,2,5], B = [2,4]
Output: [5,4]

Note:

• 1 <= A.length <= 10000
• 1 <= B.length <= 10000
• 1 <= A[i] <= 100000
• 1 <= B[i] <= 100000
• It is guaranteed that Alice and Bob have different total amounts of candy.
• It is guaranteed there exists an answer.

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Solution

• mine
  • Java
    • Runtime: 27 ms, faster than 26.21%, Memory Usage: 78.1 MB, less than 5.55% of Java online submissions

      // O(N)time
      // O(N)space
      public int[] fairCandySwap(int[] A, int[] B) {
          int[] res = new int[2];
          Set<Integer> setA = new HashSet<>();
          Set<Integer> setB = new HashSet<>();
          int sumA = 0, sumB = 0;
          for(int a : A){
              sumA+=a;
              setA.add(a);
          }
          for(int b : B){
              sumB+=b;
              setB.add(b);
          }
          int dx = (sumA - sumB) / 2;
          for(int a : A){
              if(setB.contains(a - dx)){
                  res[0] = a;
                  res[1] = a - dx;
                  break;
              }
          }
          return res;
      }
      

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• the most votes

• Runtime: 4 ms, faster than 99.65%, Memory Usage: 40.3 MB, less than 89.85% of Java online submissions

  public int[] fairCandySwap(int[] A, int[] B) {
      int sumA = 0;
      for (int value : A) {
          sumA += value;
      }
      int sumB = 0;
      for (int value : B) {
          sumB += value;
      }
      int dif = (sumA - sumB) / 2;
      int[] count = new int[100001];
      for (int i : B) {
          ++count[i];
      }
      for (int i : A) {
          int index = i - dif;
          if (index >= 0 && index < count.length && count[index] > 0) {
              return new int[]{i, index};
          }
      }
      return null;
  }
  

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