LeetCode-in-Java
1711. Count Good Meals
Medium
A good meal is a meal that contains exactly two different food items with a sum of deliciousness equal to a power of two.
You can pick any two different foods to make a good meal.
Given an array of integers deliciousness where deliciousness[i] is the deliciousness of the ith item of food, return the number of different good meals you can make from this list modulo 109 + 7.
Note that items with different indices are considered different even if they have the same deliciousness value.
Example 1:
Input: deliciousness = [1,3,5,7,9]
Output: 4
Explanation: The good meals are (1,3), (1,7), (3,5) and, (7,9). Their respective sums are 4, 8, 8, and 16, all of which are powers of 2.
Example 2:
Input: deliciousness = [1,1,1,3,3,3,7]
Output: 15
Explanation: The good meals are (1,1) with 3 ways, (1,3) with 9 ways, and (1,7) with 3 ways.
Constraints:
1 <= deliciousness.length <= 1050 <= deliciousness[i] <= 220
Solution
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
public class Solution {
public int countPairs(int[] d) {
HashMap<Integer, Integer> map = new HashMap<>();
for (int k : d) {
map.put(k, map.getOrDefault(k, 0) + 1);
}
long result = 0;
for (Iterator<Map.Entry<Integer, Integer>> it = map.entrySet().iterator(); it.hasNext(); ) {
Map.Entry<Integer, Integer> elem = it.next();
int key = elem.getKey();
long value = elem.getValue();
for (int j = 21; j >= 0; j--) {
int find = (1 << j) - key;
if (find < 0) {
break;
}
if (map.containsKey(find)) {
if (find == key) {
result += (((value - 1) * value) / 2);
} else {
result += (value * map.get(find));
}
}
}
it.remove();
}
int mod = 1_000_000_007;
return (int) (result % mod);
}
}