CORE CONCEPT — WHAT IS INPUT-OUTPUT? Input-Output is a machine-based logic puzzle. A machine takes a line of words or numbers (called INPUT). It rearranges them step by step. Each step follows a fixed hidden rule. Your job is to find that rule and answer questions about any step.
Think of it like a washing machine. You put dirty clothes in (input). Each cycle does something. After all cycles, you get clean, arranged clothes (output). ---
The rule is ALWAYS consistent. Every step follows the same pattern.
The arrangement can involve words, numbers, or both.
Common operations: shifting words/numbers left or right, arranging in ascending or descending order, alternating between smallest and largest, arranging alphabetically.
The machine usually completes in 4 to 6 steps.
Once an element is placed in its final position, it does NOT move again in later steps.
- What is Step 3 of the given input? - Which step gives a particular output? - How many steps are needed to complete the arrangement? - What is the position of a specific word in a given step? - Which step is the final output? --- TYPES OF INPUT-OUTPUT MACHINES Type 1 — Word Shift Machine: Words move one by one to the left or right end
Numbers arrange in ascending or descending order, one number per step
Smallest number goes to the left end, largest goes to the right end, alternating in each step
Words and numbers are arranged separately — words alphabetically, numbers in order. ---
Shortcut 1 — Count Elements to Find Total Steps:
Shortcut 2 — Alternating Type Formula:
If smallest goes LEFT and largest goes RIGHT alternately:
...and so on.
So for 6 elements, after 5 steps, the arrangement is complete.
Shortcut 3 — Identify the Rule in 2 Steps:
Always look at Step 1 and Step 2 carefully before doing anything else. The rule becomes 100 percent clear by Step 2. Never guess from Step 1 alone.
---
8 45 13 72 29 56
8 13 45 72 29 56
8 13 29 45 72 56
8 13 29 45 56 72 Final output after 4 steps: 8 13 29 45 56 72 (ascending order) Question: What is Step 2? Answer: 8 13 45 72 29 56 Step-by-step logic: In each step, the next smallest number from the remaining unsorted elements shifts to the correct position. Track fixed elements (underline them mentally). --- WORKED EXAMPLE 2 — ALTERNATING WORD AND NUMBER Input: mango 32 apple 17 kite 54 Rule: In odd steps, the word that comes first alphabetically moves to the leftmost position. In even steps, the largest number moves to the rightmost position.
apple mango 32 17 kite 54
apple mango 32 17 kite 54 — wait, 54 is already at the right. Let us re-read: 54 moves to the right end.
apple mango 32 17 kite 54
apple kite mango 32 17 54
apple kite mango 17 32 54
apple kite mango 17 32 54 — arrangement complete. Key learning: Always re-check if an element is already in position. Do not count it as a new step. ---
— NUMBER 1 TRAP Students assume the rule from Step 1 only and apply it wrong. Example trap: In Step 1, the smallest number moves left. Student assumes smallest always moves. But from Step 2, the rule shifts to largest moving right.
This alternating rule is the most common trap in SSC CGL input-output questions. FIX: Always verify the rule using BOTH Step 1 and Step 2 before solving. Also, students forget that already-fixed elements stay in place. They re-arrange them by mistake and get the wrong step output. --- EXAM STRATEGY 1. Read the full input and all given steps before answering. 2.
Write down Step 1 and Step 2 and find the pattern. 3. Use the total-steps formula to estimate how many steps remain. 4. Answer all 4-5 questions from the same pattern — saves huge time. 5.
Target: Solve the full set in 3 to 4 minutes maximum.
37graded MCQs · easy to hard · full solution & trap analysis · showing 20 of 37
Difficulty-graded, bookmarkable, with timed mode. Free account — no credit card.