Regarding syntax and usage of commas in c++

Question

This solution to the problem presented on https://leetcode.com/problems/two-sum/:

Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9 Output: index1=1, index2=2

by wz2326 (https://leetcode.com/discuss/58175/clean-16ms-c-solution):

vector<int> twoSum(vector<int>& nums, int target) {
    unordered_map<int, int> hash;
    vector<int> res(2, 0);
    for (int i = 0; i < nums.size(); i++) {
        if (hash.find(target - nums[i]) != hash.end()) {
            res[0] = hash[target - nums[i]], res[1] = i + 1;
            return res;
        }
        hash[nums[i]] = i + 1;
    }
}

introduces pretty strange use of commas during assignment of int values to vector elements:

res[0] = hash[target - nums[i]], res[1] = i + 1;

Does anyone know the meaning of comma here? Thanks.

It's the [comma operator](https://en.wikipedia.org/wiki/Comma_operator) — Paolo M, Oct 02 '15 at 15:09
Never write code like this. Sincerely, Everybody who will ever read your code. — Barry, Oct 02 '15 at 15:10
What is the real difference between ',' and ';' performance-wise? — Anon, Oct 02 '15 at 15:26
There is (almost certainly) no performance difference. The only difference is legibility. If you really want to put both assignments on one line (and there's no for reason to do that) it's clearer to separate them with a semicolon. — Keith Thompson, Oct 02 '15 at 15:54

Regarding syntax and usage of commas in c++

0 Answers0