3208. Alternating Groups II
There is a circle of red and blue tiles. You are given an array of integers colors
and an integer k
. The color of tile i
is represented by colors[i]
:
colors[i] == 0
means that tilei
is red.colors[i] == 1
means that tilei
is blue.
An alternating group is every k
contiguous tiles in the circle with alternating colors (each tile in the group except the first and last one has a different color from its left and right tiles).
Return the number of alternating groups.
Note that since colors
represents a circle, the first and the last tiles are considered to be next to each other.
Example 1:
Input: colors = [0,1,0,1,0], k = 3
Output: 3
Explanation:
Alternating groups:
Example 2:
Input: colors = [0,1,0,0,1,0,1], k = 6
Output: 2
Explanation:
Alternating groups:
Example 3:
Input: colors = [1,1,0,1], k = 4
Output: 0
Explanation:
Constraints:
3 <= colors.length <= 105
0 <= colors[i] <= 1
3 <= k <= colors.length
Soluton:
class Solution {
public int numberOfAlternatingGroups(int[] colors, int k) {
int n = colors.length;
// if(k<n) return 0;
int answer=0;
List<Integer> list = new ArrayList<>();
for(int i:colors) list.add(i);
for(int i=0;i<k-1;i++) list.add(colors[i]);
// System.out.println(list);
int start = 0;
int end = 1;
int len = 1;
while(start<n && end<n+k-1){
if(list.get(end)!=list.get(end-1)) {
// end++;
len++;
}
else{
start = end;
len =1;
}
if(len==k){
answer++;
start++;
len--;
}
end++;
}
return answer;
}
}