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LeetCode_169_18.java
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61 lines (51 loc) · 1.6 KB
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package Week_04.id_18;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
/**
* @author LiveForExperience
* @date 2019/6/25 19:16
*/
public class LeetCode_169_18 {
public int majorityElement(int[] nums) {
Map<Integer, Long> map = new HashMap<>();
int len = nums.length / 2;
for (Integer num: nums) {
map.compute(num, (k, v) -> v == null ? 1 : v++);
if (map.get(num) > len) {
return num;
}
}
return 0;
}
public int majorityElement1(int[] nums) {
Arrays.sort(nums);
return nums[nums.length / 2];
}
public int majorityElement2(int [] nums) {
return divideConquer(nums, 0, nums.length - 1);
}
private int divideConquer(int[] nums, int left, int right) {
if (left == right) {
return nums[left];
}
int mid = (right - left) / 2 + left;
int leftMajorityNum = divideConquer(nums, left, mid);
int rightMajorityNum = divideConquer(nums, mid + 1, right);
if (leftMajorityNum == rightMajorityNum) {
return leftMajorityNum;
}
long leftCount = count(nums, leftMajorityNum, left, mid);
long rightCount = count(nums, rightMajorityNum, mid + 1, right);
return leftCount > rightCount ? leftMajorityNum : rightMajorityNum;
}
private int count(int[] nums, int num, int left, int right) {
int count = 0;
for (int i = left; i <= right; i++) {
if (nums[i] == num) {
count++;
}
}
return count;
}
}