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Copy pathArrayQuadruplet.java
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86 lines (74 loc) · 2.62 KB
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package pramp;
import java.util.Arrays;
public final class ArrayQuadruplet {
public static final int[] EMPTY_ARRAY = new int[0];
private static int[] findArrayQuadruplet(int[] arr, int s) {
Arrays.sort(arr);
for (int i = 0; i < arr.length; i++) {
final int[] ints = threeSum(arr, s - arr[i], i);
if (ints.length > 0) {
return new int[] { arr[i], ints[0], ints[1], ints[2] };
}
}
return EMPTY_ARRAY;
}
private static int[] twoSum(int[] arr, int s, int ignoreIdx1, int ignoreIdx2) {
int start = 0;
int end = arr.length - 1;
while (start < end) {
if (start == ignoreIdx1 || start == ignoreIdx2) {
start++;
continue;
}
if (end == ignoreIdx1 || end == ignoreIdx2) {
end--;
continue;
}
if (arr[start] + arr[end] > s) {
end--;
} else if (arr[start] + arr[end] == s) {
return new int[] { arr[start], arr[end] };
} else {
start++;
}
}
return EMPTY_ARRAY;
}
private static int[] threeSum(int[] arr, int s, int ignoreIdx) {
for (int i = 0; i < arr.length; i++) {
if (i == ignoreIdx) { continue; }
final int[] ints = twoSum(arr, s - arr[i], ignoreIdx, i);
if (ints.length > 0) {
return new int[] { arr[i], ints[0], ints[1] };
}
}
return EMPTY_ARRAY;
}
private static int[] fourSum(int[] arr, int s) {
if (arr.length < 4) {
return EMPTY_ARRAY;
}
Arrays.sort(arr);
for (int i = 0; i < arr.length; i++) {
for (int j = i + 1; j < arr.length; j++) {
final int findTwoSum = s - (arr[i] + arr[j]);
int start = j + 1;
int end = arr.length - 1;
while (start < end) {
if (arr[start] + arr[end] > findTwoSum) {
end--;
} else if (arr[start] + arr[end] == findTwoSum) {
return new int[] { arr[i], arr[j], arr[start], arr[end] };
} else {
start++;
}
}
}
}
return EMPTY_ARRAY;
}
public static void main(String[] args) {
System.out.println(Arrays.toString(findArrayQuadruplet(new int[] { 4, 4, 4, 2 }, 16)));
System.out.println(Arrays.toString(fourSum(new int[] { 2, 7, 4, 0, 9, 5, 1, 3 }, 20)));
}
}