LeetCode-in-Java
2134. Minimum Swaps to Group All 1’s Together II
Medium
A swap is defined as taking two distinct positions in an array and swapping the values in them.
A circular array is defined as an array where we consider the first element and the last element to be adjacent.
Given a binary circular array nums, return the minimum number of swaps required to group all 1’s present in the array together at any location.
Example 1:
Input: nums = [0,1,0,1,1,0,0]
Output: 1
Explanation: Here are a few of the ways to group all the 1’s together:
[0,0,1,1,1,0,0] using 1 swap.
[0,1,1,1,0,0,0] using 1 swap.
[1,1,0,0,0,0,1] using 2 swaps (using the circular property of the array).
There is no way to group all 1’s together with 0 swaps.
Thus, the minimum number of swaps required is 1.
Example 2:
Input: nums = [0,1,1,1,0,0,1,1,0]
Output: 2
Explanation: Here are a few of the ways to group all the 1’s together:
[1,1,1,0,0,0,0,1,1] using 2 swaps (using the circular property of the array).
[1,1,1,1,1,0,0,0,0] using 2 swaps.
There is no way to group all 1’s together with 0 or 1 swaps.
Thus, the minimum number of swaps required is 2.
Example 3:
Input: nums = [1,1,0,0,1]
Output: 0
Explanation: All the 1’s are already grouped together due to the circular property of the array.
Thus, the minimum number of swaps required is 0.
Constraints:
1 <= nums.length <= 105nums[i]is either0or1.
Solution
public class Solution {
public int minSwaps(int[] nums) {
int l = nums.length;
int[] ones = new int[l];
ones[0] = nums[0] == 1 ? 1 : 0;
for (int i = 1; i < l; i++) {
if (nums[i] == 1) {
ones[i] = ones[i - 1] + 1;
} else {
ones[i] = ones[i - 1];
}
}
if (ones[l - 1] == l || ones[l - 1] == 0) {
return 0;
}
int ws = ones[l - 1];
int minSwaps = Integer.MAX_VALUE;
int si = 0;
int ei;
while (si < nums.length) {
ei = (si + ws - 1) % l;
int totalones;
if (ei >= si) {
totalones = ones[ei] - (si == 0 ? 0 : ones[si - 1]);
} else {
totalones = ones[ei] + (ones[l - 1] - ones[si - 1]);
}
int swapsreq = ws - totalones;
if (swapsreq < minSwaps) {
minSwaps = swapsreq;
}
si++;
}
return minSwaps;
}
}