Merge pull request matthewsamuel95#315 from varuncoc/master

made changes

Author: matthewsamuel95

Math/2Sum/2Sum.cpp

@@ -1,42 +1,52 @@
-#include<iostream>
-#include<vector>
-#include<unordered_map>
-
-using namespace std;
-
-
-vector<int> twoSum(vector<int>& nums, int target) {
-
-	unordered_map<int,int> mp;
-	vector<int> result;
-
-	for(int i=0; i < nums.size(); i++){
-		if(mp.find(target-nums[i]) != mp.end()) {
-			result.push_back(mp[target-nums[i]]);
-			result.push_back(i);
-			break;
-		}
-		else
-			mp[nums[i]] = i;
-	}
-	return result;
+#include <algorithm>
+#include <ctime>
+#include <iostream>
+#include <random>
+#include <vector>
+
+long long random_number()
+{
+    const long long min = -100'000'000'000;
+    const long long max =  100'000'000'000;
+    static std::mt19937_64 gen(std::time(nullptr));
+    static std::uniform_int_distribution<long long> dist(min, max);
+    return dist(gen);
 }
 
+bool is_sum_exist(const std::vector<long long>& data, long long x)
+{
+    auto j = std::lower_bound(data.begin(), data.end(), x)  -  data.begin();
+    decltype(j) i = 0;
+    if(j == data.size()) --j;
+    while (i < j)  {
+        long long sum = data[i]+data[j];
+             if (sum == x)  return true;
+        else if (sum >  x)  --j;
+        else                ++i;
+    }
+    return false;
+}
 
-int main() {
-	
-	vector<int> nums;
-
-	nums.push_back(2);
-	nums.push_back(7);
-	nums.push_back(11);
-	nums.push_back(15);
-
-	int target = 9;
-
-	vector<int> result = twoSum(nums,target);
-
-	cout << result[0] << " " << result[1] << endl;
-
-	return 0;
+int main()
+{
+    const std::size_t data_size = 1'000'000;
+    const std::size_t requests = 100000;
+    std::cin.sync_with_stdio(false); //In case I need to output actual numbers
+
+    //creating dataset
+    std::vector<long long> data(data_size);
+    std::generate_n(data.begin(), data.size(), random_number);
+    std::sort(data.begin(), data.end());
+
+    //creating values we will search sum of
+    std::vector<long long> rand_values(requests);
+    std::generate_n(rand_values.begin(), rand_values.size(), random_number);
+    std::cout << "done" << std::endl;
+
+    long long counter = 0;
+    for(auto t: rand_values) {
+        if(is_sum_exist(data, t))
+            ++counter;
+    }
+    std::cout << counter;
 }

Math/3Sum/3Sum.cpp

@@ -1,33 +1,34 @@
-#include <iostream>
-#include <algorithm>
-#include <unordered_map>
-
+#include<algorithm>
+#include<vector>
 using namespace std;
 
-bool find_triplet( int arr[], int arr_size, int value ) {
-	unordered_map<int, int> map;
-	
-	for ( int i = 0; i < arr_size; i++ )
-		map[arr[i]] = i;
-		
-	for ( int i = 0; i < arr_size - 1; i++ )
-		for ( int j = i + 1; j < arr_size; j++ ) {
-			int sum = value - ( arr[i] + arr[j] );
+class Solution {
+public:
+    vector<vector<int> > threeSum(vector<int> &num) {
+        vector<vector<int> > ans;
+        if(num.size()<3) return ans;
+        		
+		sort(num.begin(), num.end());
+
+		for (size_t i = 0; i < num.size() - 2; i++) {
+            if(i && num[i]==num[i-1]) continue;
 
-			if ( map.find( sum ) != map.end() )
-				if ( map[sum] != i && map[sum] != j ) {
-					cout << '(' << arr[i] << ", " << arr[j] << ", " << sum << ')' << endl; 
-					return true;
-				}
+            size_t a = i + 1, b = num.size() - 1;
+			while (a < b) {
+                if(a>i+1 && num[a]==num[a-1])           { a++; continue; }
+                if(b<num.size()-1 && num[b]==num[b+1])  { b--; continue; }
+				
+                int sum2 = num[a] + num[b];
+				if (sum2 == -num[i]) {
+					int sol[3] = { num[i], num[a], num[b] };
+					ans.push_back(vector<int> (sol, sol + 3));
+					a++, b--;
+				} else if (sum2 < -num[i])
+					a++;
+				else if (sum2 > num[i])
+					b--;
+			}
 		}
-	return false;
-}
-
-int main()
-{
-	int arr[] = { 2, 7, 4, 0, 9, 5, 1, 3 };
-	int arr_size = sizeof( arr ) / sizeof( arr[0] );
-	int value = 10;
-	
-	return find_triplet( arr, arr_size, value );
-}
+		return ans;
+	}
+};