# 2134. Minimum Swaps to Group All 1's Together II
###### tags: `Leetcode` `Medium` `Sliding Window`
Link: https://leetcode.com/problems/minimum-swaps-to-group-all-1s-together-ii/description/
## 思路
当遇到circular array的问题时，可以append the array to itself 这样就可以不管circular array的部分
固定长度的sliding window 长度为nums含有的1的个数```cntOnes```
找到sliding window里最多有几个1```maxOnesInWindow```

## Code

class Solution {
public int minSwaps(int[] nums) {
int cntOnes = 0;
for(int num:nums) if(num==1) cntOnes++;
int n = nums.length;
int[] nums2 = new int[n*2];
for(int i=0; i<2*n; i++){
nums2[i] = nums[i%n];
}
int currCntOnes = 0;
int maxOnesInWindow = 0;
for(int i=0; i<2*n; i++){
if(i>=cntOnes && nums2[i-cntOnes]==1) currCntOnes--;
if(nums2[i]==1) currCntOnes++;
maxOnesInWindow = Math.max(maxOnesInWindow, currCntOnes);
}
return cntOnes-maxOnesInWindow;
}
}

class Solution:
def minSwaps(self, nums: List[int]) -> int:
ones = nums.count(1)
nums = nums+nums
currOnes = maxCntOnes = 0
for i in range(len(nums)):
if i>=ones and nums[i-ones]==1: currOnes -= 1
if nums[i]==1: currOnes += 1
maxCntOnes = max(maxCntOnes, currOnes)
return ones-maxCntOnes