561.array-partition-i.cpp

/*
 * [561] Array Partition I
 *
 * https://leetcode.com/problems/array-partition-i/description/
 *
 * algorithms
 * Easy (67.35%)
 * Total Accepted:    112.7K
 * Total Submissions: 167.3K
 * Testcase Example:  '[1,4,3,2]'
 *
 *
 * Given an array of 2n integers, your task is to group these integers into n
 * pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of
 * min(ai, bi) for all i from 1 to n as large as possible.
 *
 *
 * Example 1:
 *
 * Input: [1,4,3,2]
 *
 * Output: 4
 * Explanation: n is 2, and the maximum sum of pairs is 4 = min(1, 2) + min(3,
 * 4).
 *
 *
 *
 * Note:
 *
 * n is a positive integer, which is in the range of [1, 10000].
 * All the integers in the array will be in the range of [-10000, 10000].
 *
 *
 */
class Solution {
 public:
  int arrayPairSum(vector<int>& nums) {
    std::sort(nums.begin(), nums.end());
    int sum = 0;
    for (int i = 0; i < nums.size(); ++i) {
      if (!(i % 2)) {
        sum += nums[i];
      }
    }
    return sum;
  }
};