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954.java
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954.java
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__________________________________________________________________________________________________
sample 3 ms submission
class Solution {
public boolean canReorderDoubled(int[] A) {
int[] countNum = new int[20001];
for (int a : A) {
countNum[a + 10000] += 1;
}
for (int i = 1; i <= 10000; i++) {
if (countNum[10000 + i] > 0){
if (countNum[10000 + i * 2] >= countNum[10000 + i]) {
countNum[10000 + i * 2] -= countNum[10000 + i];
} else {
return false;
}
}
if (countNum[10000 - i] > 0) {
if (countNum[10000 - i * 2] >= countNum[10000 - i]) {
countNum[10000 - i * 2] -= countNum[10000 - i];
} else {
return false;
}
}
}
return true;
}
}
__________________________________________________________________________________________________
sample 40604 kb submission
class Solution {
public boolean canReorderDoubled(int[] A) {
// count[x] = the number of occurrences of x in A
Map<Integer, Integer> count = new HashMap();
for (int x: A)
count.put(x, count.getOrDefault(x, 0) + 1);
// B = A as Integer[], sorted by absolute value
Integer[] B = new Integer[A.length];
for (int i = 0; i < A.length; ++i)
B[i] = A[i];
Arrays.sort(B, Comparator.comparingInt(Math::abs));
for (int x: B) {
// If this can't be consumed, skip
if (count.get(x) == 0) continue;
// If this doesn't have a doubled partner, the answer is false
if (count.getOrDefault(2*x, 0) <= 0) return false;
// Write x, 2*x
count.put(x, count.get(x) - 1);
count.put(2*x, count.get(2*x) - 1);
}
// If we have written everything, the answer is true
return true;
}
}
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