143 lines
4.2 KiB
C#
143 lines
4.2 KiB
C#
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public class Solution
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{
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record struct TwoSumSource(int A, int B)
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{
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public override string ToString()
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{
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return $"({A}+{B}={A + B})";
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}
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}
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record struct AnswerRow(int? N0 = null, int? N1 = null, int? N2 = null, int? N3 = null)
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{
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public void PushNum(int num)
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{
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if (N0 == null)
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{
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N0 = num;
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}
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else if (N1 == null)
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{
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N1 = num;
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if (N0 > N1)
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{
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(N0, N1) = (N1, N0);
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}
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}
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else if (N2 == null)
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{
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N2 = num;
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if (N1 > N2)
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{
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(N1, N2) = (N2, N1);
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}
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if (N0 > N1)
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{
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(N0, N1) = (N1, N0);
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}
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}
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else if (N3 == null)
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{
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N3 = num;
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if (N2 > N3)
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{
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(N2, N3) = (N3, N2);
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}
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if (N1 > N2)
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{
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(N1, N2) = (N2, N1);
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}
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if (N0 > N1)
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{
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(N0, N1) = (N1, N0);
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}
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}
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else if (num < N3)
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{
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N3 = num;
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if (N2 > N3)
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{
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(N2, N3) = (N3, N2);
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}
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if (N1 > N2)
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{
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(N1, N2) = (N2, N1);
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}
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if (N0 > N1)
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{
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(N0, N1) = (N1, N0);
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}
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}
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}
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}
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public IList<IList<int>> FourSum(int[] nums, int target)
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{
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var dict = new Dictionary<int, int>();
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// суммы из двух слагаемых, все возможные
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var twoSums = new Dictionary<long, HashSet<TwoSumSource>>();
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for (var i = 0; i < nums.Length; i++)
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{
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var num1 = nums[i];
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dict.TryAdd(num1, 0);
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dict[num1]++;
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for (var j = i + 1; j < nums.Length; j++)
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{
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var num2 = nums[j];
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var sum = num1 + num2;
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twoSums.TryAdd(sum, new HashSet<TwoSumSource>());
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twoSums[sum].Add(new TwoSumSource() { A = num1, B = num2 });
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}
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}
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var rows = new HashSet<AnswerRow>();
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// словарь для требуемоего количества чисел
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var needDict = new Dictionary<int, int>();
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foreach (var kp1 in dict)
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{
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var needThreeSum = target - kp1.Key;
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needDict.TryAdd(kp1.Key, 0);
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needDict[kp1.Key]++;
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foreach (var kp2 in dict)
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{
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needDict.TryAdd(kp2.Key, 0);
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needDict[kp2.Key]++;
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var needTwoSum = (long)needThreeSum - kp2.Key;
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if (twoSums.TryGetValue(needTwoSum, out var curTwoSums))
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{
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foreach (var curTwoSum in curTwoSums)
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{
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needDict.TryAdd(curTwoSum.A, 0);
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needDict[curTwoSum.A]++;
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needDict.TryAdd(curTwoSum.B, 0);
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needDict[curTwoSum.B]++;
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if (needDict.All(kp => dict[kp.Key] >= kp.Value))
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{
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var row = new AnswerRow();
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row.PushNum(kp1.Key);
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row.PushNum(kp2.Key);
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row.PushNum(curTwoSum.A);
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row.PushNum(curTwoSum.B);
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rows.Add(row);
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}
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needDict[curTwoSum.A]--;
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needDict[curTwoSum.B]--;
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}
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}
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needDict[kp2.Key]--;
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}
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needDict.Clear();
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}
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var answer = new List<IList<int>>(rows.Count);
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foreach (var row in rows)
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answer.Add(new List<int> { row.N0!.Value, row.N1!.Value, row.N2!.Value, row.N3!.Value });
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return answer;
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}
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} |