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# Partition Array

## 题目描述

Given an array nums of integers and an int k, partition the array (i.e move the elements in "nums") such that:
All elements < k are moved to the left
All elements >= k are moved to the right
Return the partitioning index, i.e the first index i nums[i] >= k.

## 代码

### Approach #1 单指针索引交换

public class Solution {
public int partitionArray(int[] nums, int k) {
int right = 0;
int size = nums.length;
for (int i = 0; i < size; i++) {
if (nums[i] < k) {
if (i != right) {
int temp = nums[i];
nums[i] = nums[right];
nums[right] = temp;
}
++right;
}
}
return right;
}
}

### Approach #2 双指针交换

public class Solution {
public int partitionArray(int[] nums, int k) {
int left = 0;
int right = nums.length - 1;
while (left <= right) {
while (left <= right && nums[left] < k) left++;
while (left <= right && nums[right] >= k) right--;
if (left <= right) {
int temp = nums[left];
nums[left] = nums[right];
nums[right] = temp;
++left;
--right;
}
}
return left;
}
}