Find pairs equal zero -- Paypal_csdn find the pairs-优快云博客

本文提供了一种算法，用于在两个等长整数数组中找到所有和为零的元素配对。该算法使用哈希集合来高效地识别符合条件的配对，避免了使用数组索引进行交叉检查的需求。

Problem

Given 2 equal-length arrays of integers, find pairs, one from each array, that sum to 0.

-- note that one wrinkle of this problem over the more usual form, which is to do this in a single array,

is that you can't use the indexes / iterators crossing each other to know to stop,

rather their /values/ have to cross (if you're doing it right, at or near 0).

Solution

#include <iostream>

#include <iomanip>

#include <hash_set>

using namespace std;

void FindPairsEqualZero(int *arr1, int* arr2, int len)

{

hash_set<int> h1, h2;

for(int i = 0; i < len; ++i){

h1.insert(arr1[i]);

h2.insert(arr2[i]);

}

for(hash_set<int>::iterator it = h1.begin(); it != h1.end(); ++ it){

if(h2.find(-*it) != h2.end()){

cout << "(" << setw(4) << *it << ", ";

cout << setw(4) << -*it << ")" << endl;

}

int main(int argc, char* argv[])

{

int *arr1, *arr2;

for(int i = 1; i < 21; ++i){

arr1 = new int[i];

arr2 = new int[i];

for(int j = 0; j < i; ++j){

arr1[j] = rand() % i - i / 2;

arr2[j] = rand() % i - i / 2;

}

cout << "Array 1:" << endl;

for(int j = 0; j < i; ++j){

cout << setw(4) << arr1[j];

}

cout << endl;

cout << "Array 2:" << endl;

for(int j = 0; j < i; ++j){

cout << setw(4) << arr2[j];

}

cout << endl;

FindPairsEqualZero(arr1, arr2, i);

cout << "-------------------------------------------";

}

return 0;

}

Output

Array 1:

0

Array 2:

0

( 0, 0)

-------------------------------------------

Array 1:

-1 0

Array 2:

-1 -1

-------------------------------------------

Array 1:

-1 0 1

Array 2:

-1 1 1

( -1, 1)

( 1, -1)

-------------------------------------------

Array 1:

-1 -1 1 1

Array 2:

1 1 0 -2

( -1, 1)

-------------------------------------------

Array 1:

-1 0 0 -1 1

Array 2:

2 1 0 -1 -2

( -1, 1)

( 0, 0)

( 1, -1)

-------------------------------------------

Array 1:

2 2 0 2 -2 2

Array 2:

-3 -3 1 -2 -3 0

( 2, -2)

( 0, 0)

-------------------------------------------

Array 1:

1 2 -3 -2 1 -3 0

Array 2:

-1 -1 1 -2 -2 1 -3

( 1, -1)

( 2, -2)

-------------------------------------------

Array 1:

-1 -3 0 2 -4 -4 -4 2

Array 2:

1 -2 -1 -2 -2 2 -4 1

( -1, 1)

( 2, -2)

-------------------------------------------

Array 1:

1 3 -1 -1 -4 -4 -4 3 4

Array 2:

2 1 2 -2 1 -3 1 1 -3

( 3, -3)

( -1, 1)

-------------------------------------------

Array 1:

-1 1 2 3 4 -2 4 -1 2 -2

Array 2:

4 -2 3 -3 -4 0 3 -5 1 1

( -1, 1)

( 2, -2)

( 3, -3)

( 4, -4)

-------------------------------------------

Array 1:

0 2 -5 -2 -1 1 4 -2 0 0 -1

Array 2:

-3 4 5 3 -4 -3 -3 1 4 2 1

( -5, 5)

( -2, 2)

( -1, 1)

( 4, -4)

-------------------------------------------

Array 1:

3 4 -3 1 -5 3 -1 -5 -1 -4 -4 3

Array 2:

-2 4 5 3 5 -3 -1 -4 -6 4 4 2

( -5, 5)

( 3, -3)

( -4, 4)

( 4, -4)

( -3, 3)

( 1, -1)

-------------------------------------------

Array 1:

-3 -3 -3 6 1 3 -5 2 -5 1 3 6 -6

Array 2:

-6 -2 -4 4 3 5 -5 -6 3 4 1 -1 -4

( -3, 3)

( 6, -6)

( 1, -1)

( -5, 5)

( 2, -2)

-------------------------------------------

Array 1:

4 -7 5 4 -3 1 6 -5 0 -6 0 -1 6 -1

Array 2:

4 1 1 -2 4 6 6 2 1 -7 0 6 -7 0

( 0, 0)

( -6, 6)

( -1, 1)

-------------------------------------------

Array 1:

7 2 -3 -7 -4 6 -3 1 -4 -7 1 7 -3 5 6

Array 2:

6 7 -5 3 -4 5 1 -7 -4 4 4 1 0 5 0

( 7, -7)

( -3, 3)

( 5, -5)

( -7, 7)

( -4, 4)

-------------------------------------------

Array 1:

-2 6 -2 -1 -4 2 -8 0 2 3 5 -4 1 -6 -3 -3

Array 2:

-5 1 7 0 -1 2 -1 -2 -2 -7 6 0 6 3 -5 4

( -2, 2)

( -1, 1)

( -4, 4)

( 2, -2)

( 0, 0)

( 5, -5)

( 1, -1)

( -6, 6)

( -3, 3)

-------------------------------------------

Array 1:

4 1 8 0 3 -3 -2 -4 0 -1 -2 -2 -4 -8 -7 -3 -3

Array 2:

3 -6 3 1 -8 6 -7 3 -8 2 0 1 4 -6 7 5 7

( -4, 4)

( 0, 0)

( 8, -8)

( -3, 3)

( -2, 2)

( -1, 1)

( -7, 7)

-------------------------------------------

Array 1:

5 -2 4 1 2 -2 -8 4 3 4 -6 -1 -1 8 -3 5 -1 2

Array 2:

-2 -1 -3 0 -6 -5 -8 4 -2 2 -5 4 1 3 -8 -2 -4 -8

( 5, -5)

( -2, 2)

( 4, -4)

( 1, -1)

( 2, -2)

( 3, -3)

( -1, 1)

( 8, -8)

( -3, 3)

-------------------------------------------

Array 1:

-3 -9 -1 -9 2 1 -3 7 -5 -3 -8 8 6 -8 1 5 -9 0 -7

Array 2:

-1 7 -2 7 -2 5 -7 -3 5 -3 7 9 1 8 -6 6 1 7 6

( -9, 9)

( -1, 1)

( 7, -7)

( 2, -2)

( 1, -1)

( -5, 5)

( -8, 8)

( 6, -6)

( -7, 7)

-------------------------------------------

Array 1:

-3 8 -8 7 4 4 2 3 -3 8 3 -7 2 -8 3 -8 -3 -7 -7 -9

Array 2:

-5 1 -5 4 -6 4 9 0 7 7 0 -2 -5 -10 -3 9 -5 -6 2 -9

( -9, 9)

( 2, -2)

( 3, -3)

( -7, 7)

-------------------------------------------

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