3. Two Sum

Hash Table/C++/3_Two_Sum.cpp

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+/*
+
+Problem: Two Sum
+
+Description:
+Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
+It is assumed that each input would have exactly one solution, and the same element is not used twice.
+
+This solution returns the indices of the array nums that sum up to obtain target in random order.
+
+Note:
+2 <= nums.length <= 104
+-109 <= nums[i] <= 109
+-109 <= target <= 109
+Only one valid answer exists.
+
+*/
+
+#include<iostream>
+#include<bits/stdc++.h>
+#include<vector>
+
+using namespace std;
+
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+        vector<int> ans;
+        int l;
+        l=nums.size(); // l->size of the input array.
+
+
+        for(int i=0;i<(l-1);i++) {  // This loop i goes from 0 to l-1.
+            for(int j=(i+1);j<l;j++) { // This loop goes from i+1 to l.
+
+                int sum = nums[i]+nums[j];
+                // If sum = target, add indices to answer array, also breaks the loop.
+                if(sum==target) {
+                    ans.push_back(i);
+                    ans.push_back(j);
+                    break;
+                }
+            }
+        }
+        return ans;
+    }
+};
+
+int main() {
+
+	int t;
+	cout<<"Enter number of testcases: ";
+	cin>>t; // Number of testcases.
+
+	for(int tc=0;tc<t;tc++) {
+
+		Solution* s = new Solution;
+
+		cout<<"Enter the size of array: ";
+		int sz;
+		cin>>sz; //Size of the input array
+
+		vector<int> ar(sz);
+
+		cout<<"Enter array values: "; 
+		// Array values
+		for(int a=0;a<sz;a++) {
+			cin>>ar[a];
+		}
+
+		// Target
+		cout<<"Enter target: ";
+		int tar;
+		cin>>tar;
+
+		vector<int> answer;
+
+		answer=s->twoSum(ar,tar);
+
+		// Outputs the answer
+		cout<<"Output: ";
+		for(int o=0;o<(answer.size());o++) {
+			cout<<answer[o]<<" ";
+		}
+		cout<<endl;
+	}
+	return 0;
+}
+
+/*
+//Accepted
+
+First line represents the number of testcases.
+First input of every line represents the size of array. let's say n.
+Next n elements of the same line represent the array elements.
+Last element of every line represnts the corresponding target.
+
+SAMPLE INPUT:
+3                       -> Number of testcases
+4 2 7 11 15 9           -> First testcase.  
+3 3 2 4 6
+2 3 3 6
+
+SAMPLE OUTPUT: (Exclusive of interactive statements)
+0 1                     
+1 2
+0 1
+
+Explanation:
+Testcase 1:
+Input array(say nums): [2 7 11 15]. Target=9
+Output array: [0 1] which represent the indices of the input array that sum up to the target i.e., nums[0]+nums[1]=9 (Because 2+7=9).
+
+Same for all the testcases.
+
+Time Complexity: O(n^2)  
+n = Size of the input array
+
+*/