setup bloom time for each flower, dp[i] = n means for flower index of i is bloom at nth day.

setup high = low + k +1;

when dp[high] and dp[low] is the lowest two values index from low to high. means low to high is a valid answer.

for i (low < i < high) , if dp[i] < dp[low] OR dp[i] < dp[high] , means low to high is not a valid answer,

when dp[i] > dp[high] && dp[i] < dp[low] , means i is not a valid low index, so low = i+1, high = low+k+1

when dp[i] < dp[high] , means i is possible a valid answer. . so set low = i, high = low+k +1

```
public class Solution {
public int KEmptySlots(int[] flowers, int k) {
var len = flowers.Length;
var dp = new int[len+1];
for(int i = 0;i<len;i++){
dp[flowers[i]] = i+1;
}
int low = 1;
int high = low+k+1;
int result = len+1;
while(high <= len){
bool valid = true;
for(int i = low+1;i<high;i++){
if(dp[i] < dp[low] || dp[i] < dp[high]){
if(dp[i] > dp[high]){
low = i+1;
}else{
low = i;
}
high = low+k+1;
valid = false;
break;
}
}
if(valid){
result = Math.Min(result,Math.Max(dp[low],dp[high]));
low = high;
high = low+k+1;
}
}
return result > len ? -1 : result;
}
}
```