Crack the Code for Number Lock Puzzle with 162 in Minimum Steps

Submitted by Atanu Chaudhuri on Mon, 18/08/2025 - 15:25

Given 5 clues each with a hint code and digit and position correctness information. Crack the minimal step solution to the 3 digit number lock puzzle 162.

Challenge to Crack the Code for Number Lock Puzzle with 162 in Minimum Steps: The Puzzle

Find the 3 digit code from the five clues to open the number lock in minimum steps:

Clue 1: Code 1 6 2 : One digit right and in right position.

Clue 2: Code 2 3 4 : One digit right and in right position.

Clue 3: Code 1 7 3 : One digit correct but in wrong place.

Clue 4: Code 9 8 5 : Nothing is correct.

Clue 5: Code 5 7 4 : Two digits right, one in right place, the other in wrong place.

Time for the minimum clue, minimum step solution: 10 minutes.

Hint: Find and use the key patterns of a digit appearing in multiple clues.

Minimum Clue, Minimum Step Solution to the 3 Digit Number Lock Puzzle 162 with 5 Clues

The most reasonable first step is to find a correct or an incorrect digit as, attempts to find the correct place before finding the correct digit makes no sense.

Step 1: Identify a correct or an incorrect digit

The common pattern that identifies an incorrect digit is position and correctness conflict when one correct digit appears in two clues in the same position, but with conflict in their position descriptions.

Such a pair of clues is Clues 1 and 3.

Clue 1: Code 1 6 2 : One digit right and in right position.

Clue 3: Code 1 7 3 : One digit correct but in wrong place.

Digit 1 appears in the leftmost position in both the clues with same positive correctness but different position descriptions. Both cannot be true.
Digit 1 is the first incorrect digit you identify.

Step 2: Identify the second correct digit and placement of one

Looking for the same pattern of conflicting correctness and placement descriptions, now Clues 1 and 2 appear in your radar.

Clue 1: Code 1 6 2 : One digit right and in right position.

Clue 2: Code 2 3 4 : One digit right and in right position.

In both, digit 2 is common, both states one right digit in right place. As 2 is in rightmost position in Clue 1 and leftmost in Clue 2, it cannot be the single right digit in both.
2 is the second incorrect digit and 6 is the correct digit in Clue 1 in middle position (both 1 and 2 wrong).
Lock opening code: [ ? 6 ? ].
One of 3 and 4 is correct in Clue 2. But 3 in Clue 2 is in positional conflict with 6 in lock opening code.
4 is the only correct digit in Clue 2 with digit 3 wrong.
Lock opening code [ ? 6 4 ]. Potential for both the clues exhausted.

Step 3: Identify the third correct digit to crack the code

Choose Clue 3 as it includes two wrong digits 1 and 3 wrong - link reference technique.

Clue 3: Code 1 7 3 : One digit correct but in wrong place.

As digits 1 and 3 are wrong, digit 7 is the third correct digit in the leftmost place.
The lock opening code is [ 7 6 4 ].

Solution in 3 steps using 3 clues. This should be your minimum clue, minimum step solution.

Clues 4 and 5 are not used.

This is a measure of efficiency of the solution, but being free resources now, these can be used (following the inventive principle of free resource use) for verification of the lock opening code 764.

Clue 4: Code 9 8 5 : Nothing is correct.

None of the three wrong digits are in the lock opening code, and the clue verifies it by not violating the code. This is a negative type of verification.

Clue 5: Code 5 7 4 : Two digits right, one in right place, the other in wrong place.

The two correct digits common with your code 764 are 7 and 4, 7 in wrong place and 4 in its place. Code verified.

Explore the solution steps starting with the "Nothing is correct" Clue 4. Though this clue identifies three digits as wrong at one go, unfortunately, none of the three wrong digits except 5 appears in any of the other four clues.

Lessons from the solution

Objective for the first step and strategic insight: Must be to find one or more than one incorrect digit. Avoid the clue with all digits wrong if its wrong digits are nearly absent in the other four clues. With this strategic insight, Clue 4 was avoided in the first step and other clinching digits patterns in multiple clues used.
Position and correctness conflict of a single digit common in two clues, described as correct in both but with conflicting position descriptions. This identifies the digit as incorrect to give you the first breakthrough. Clues 1 and 3 together identified digit 1 as incorrect.

This type of position and correctness conflict of digit pattern occurs frequently in number lock puzzles.
This technique of using two clues instead of the "nothing is correct" clue has the added advantage of future promise in identifying rest of the four digits in the two clues as correct or incorrect.
This often used breakthrough digit pattern must have one of the two clues positive (clues are of two types - positive with none of the correctness and placement descriptions stating "wrong" and negative with at least one description stating "wrong").

Position and correctness conflict of type 2 occurs in two clues with one digit common in two different positions, but both the clues stating one digit right and in right place (both the clues must be of positive type).

The second breakthrough in getting the second incorrect digit 1 from Clues 1 and 2 used this special pattern.

Extraction of maximum information in an analysis is vitally important in achieving quick and elegant success.

Adherence to this maxim is exemplified in analyzing Clues 1 and 2 in step 2.
The first goal to identify the second wrong digit 2 identified the first correct digit 6 in the middle.
This produced a positional conflict between 6 and probable correct digit 3 in Clue 2 identifying it as wrong with an additional discovery of the second correct digit 4 in the rightmost place in the correct code - a major result out of one step of analysis.

Link reference technique that identified a pair of incorrect digits in a clue and helped to crack the code.

Overall, it has been an exercise of choosing the most suitable combination of clues individually or together for the series of breakthroughs following a strategic approach.

Coupled with the ability to identify a useful pattern and use the pattern for a breakthrough, the strategic analytic approach could deliver the minimum clue, minimum step solution with no complications or random steps.

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