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SUMFOUR - 4 values whose sum is 0 |
The SUM problem can be formulated as follows: given four lists A, B, C, D of integer values, compute how many quadruplet (a, b, c, d ) belongs to A x B x C x D are such that a + b + c + d = 0 . In the following, we assume that all lists have the same size n.
Input
The first line of the input file contains the size of the lists n (this value can be as large as 4000). We then have n lines containing four integer values (with absolute value as large as 228 ) that belong respectively to A, B, C and D.
(Edited: n <= 2500)
Output
Output should be printed on a single line.
Example
Input: 6 -45 22 42 -16 -41 -27 56 30 -36 53 -37 77 -36 30 -75 -46 26 -38 -10 62 -32 -54 -6 45 Output: 5
| Added by: | Abhilash I |
| Date: | 2007-02-06 |
| Time limit: | 1.419s |
| Source limit: | 50000B |
| Memory limit: | 1536MB |
| Cluster: | Cube (Intel G860) |
| Languages: | All except: ERL JS-RHINO NODEJS PERL6 VB.NET |
| Resource: | South western 05-06 |
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2020-04-21 23:12:31
It can be solved using hashing. Instead of using STL try implementing your own hash map:) |
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2020-04-01 16:01:14
Since you have come to comments for help, use equal_range in c++ |
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2020-03-09 07:36:55
accepted in one submission , make lhs and rhs two array and then sort ,and search for each lhs the upper and lower bound in rhs..... |
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2020-02-27 19:30:05
holding the meet in the middle concept, first tried with unordered map but got TLE, then tried with two pointers and got AC |
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2020-01-31 12:39:10
Has anybody done this in java? |
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2019-12-26 12:52:53
ABCDEF...a similar problem to this one... upper_bound lower_bound didn't work in this as it did in ABCDEF....passed it using equal_range.... |
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2019-11-03 19:50:54
Using STL equal_range |
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2019-07-24 04:56:34
Sadly, some datasets have nearly no zero-summing quadruplets, rendering a large assortment of possible optimizations useless. Most people commenting here seem to confuse optimization with not doing stupid stuff, and noone claiming to have done it in O(n^2) has runtime to prove it. I'm still bothered to find the efficient approach candide hinted to, but other than that the problem seems like a waste of time after getting the green bar. |
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2019-06-21 11:18:25
Just use equal range in place of unordered_map. Although the complexity was better using unordered_map but equal_range get AC whereas unordered_map gave TLE. |
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2019-06-04 12:10:34
tle for O(n*n) also,using unordered map edit:equal_range gave ac despite being O(n*n*logn) Last edit: 2019-06-04 12:39:04 |
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