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].
Java:
class Solution {
public int arrayPairSum(int[] nums) {
int sum = 0;
quickSort(nums,0,nums.length - 1);
for (int i = 0; i < nums.length; i += 2) {
sum += nums[i];
}
return sum;
}
public void quickSort(int[] array, int low, int high) {
if (low > high) return;
int i = low;
int j = high;
int temp = array[low];
while (i != j) {
while (array[j] >= temp && i < j) {
j--;
}
while (array[i] <= temp && i < j) {
i++;
}
if (array[i] > array[j]) {
int tem = array[i];
array[i] = array[j];
array[j] = tem;
}
}
array[low] = array[i];
array[i] = temp;
quickSort(array,low,j - 1);
quickSort(array,i + 1,high);
return;
}
}