Array: [-4, -1, 0, 1, 3, 5] #already sorted(ordered) Step 1: Fix the number -4 😎Fix means take as a constant - 4 or u can say freeze -4,Don't move it 👉🏽3-Sum goal is: a + b + c = 0 substitute -4 =a: -4 + b + c = 0 => b + c = 4 :) Target for the remaining two numbers sum = 4 Step 2: Choose where b and c can come from: We mustn't reuse -4 , so we search to the right👇 [-4 | -1, 0, 1, 3, 5]
↑ ↑ ↑ ↑ ↑ now pointer is doing this: left = -1, right = 5. then -1 + 5 = 4✅ :- b = -1 & c = 5 Step 4: Build the triplet: and don't forget the fixed number😀-4 => -4 + (-1) + 5 = 0 👏 Valid triplet found: (-4, -1, 5) Step 5: What happen next? After then finding a valid pair: -move both pointer: means the left to the right and the right to the left at the same time. & If there's duplicate skip New pointers: left = 0, right = 3. 0 + 3 !=4(target value). So since Sum < target move the left to the right. 1 + 3 = 4 👏Again a valid triplet found: (-4, 1, 3) keep in mind: if left and right crossed each others stop the condition. (left = 3 then right = 1)CROSSED CONDITIONS⚠️ FINAL RESULT FOR FIXED -4 Valid triplet: (-4, -1, 5) & (-4, 1, 3) Generally: 3-Sum = Freeze one number → solve a 2-sum problem beside it.

Don't forget about two pointer👌 In simple the program is talks about fixing (keep constant each elements if it's true and find sum of other two values that equal to target. Therefore, fixed value -4 and -1. here algorithm say this's VALID TRIPLET but for others since they're not equal to their target value.

if he said now I'm in class but there's no anyone. I need all of u to back to class early😔

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