algorithm - Find largest product of negative numbers in Java -

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i taking semi-advanced class in java. taught myself javascript hobby, i'm not real beginner, i'm not experienced when comes making algorithms. have homework problem do. goes along lines of: given n positive integers, n >= 5 find largest product possible picking 2 (not consecutive) numbers factors.

for example, if input is: 3 6 0 10 4, output should 60.

this seemed easy. picked largest 2 , multiplied them:

system.out.println("how many numbers give me?"); int n = sc.nextint(); if (n < 5) throw new error("n must @ least 5"); system.out.println("enter numbers"); int max1 = 0, max2 = 0; (int = 0; < n; ++i) {     int newint = sc.nextint();     if (newint > max1) {         max2 = max1;         max1 = newint;     } else if (newint > max2) {         max2 = newint;     } } system.out.println("the largest product " + (max1 * max2));

this worked perfectly. now, there "bonus" or extended problem after 1 (optional). decided try it. problem similar: given n (not positive) integers, find largest product possible picking 2 (not consecutive) numbers factors. program should run in reasonable amount of time, given 5 <= n <= 25

the problem old program fail inputs -6 -5 3 0 4. ouput 12 when correct answer 30. decided check absolute values instead of actual values, negative numbers included. code went like:

system.out.println("how many numbers give me?"); int n = sc.nextint(); if (n < 5) throw new error("n must @ least 5"); system.out.println("enter numbers"); int max1 = 0, max2 = 0; (int = 0; < n; ++i) {     int newint = sc.nextint(), absvalue = math.abs(newint);     if (absvalue > math.abs(max1)) {         max2 = max1;         max1 = newint;     } else if (absvalue > math.abs(max2)) {         max2 = newint;     } } system.out.println("the largest product " + (max1 * max2));

this worked -6 -5 3 0 4, correctly giving 30 failed -6 -3 1 5 4. gave answer of -30 incorrect.

i tried brute force solution, (checking every possible product) worked n = 5 requires n! iterations, means takes long time n = 25. i'm stumped on how solve problem. thank in advance.

the problem checking absolute value throws away information may negative. need either 2 positive or 2 negative numbers.

the simplest way achieve scan through, find 2 smallest , 2 largest numbers.

multiple 2 smallest. multiply 2 largest. whichever of bigger result.


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