2024/11/6 灵茶题单 滑动窗口 恰好型滑动窗口

src/main/java/com/cool/ling_cha_mount/sliding_windows/Num1248.java

@@ -0,0 +1,58 @@
+package com.cool.ling_cha_mount.sliding_windows;
+
+/**
+ * @author : Cool
+ * @date: 2024/11/07
+ * 1248. 统计「优美子数组」
+ */
+public class Num1248 {
+    /**
+     * @Author Cool
+     * @Date 17:43 2024/11/7
+     * 前缀和
+     **/
+    public int numberOfSubarrays1(int[] nums, int k) {
+        int res = 0;
+        int count=0;
+        int[] arr = new int[nums.length + 1];
+        arr[0]=1;
+        for(int num:nums){
+            count+=num&1;
+            arr[count]++;
+            if(count>=k){
+                res+=arr[count-k];
+            }
+        }
+        return res;
+    }
+    /**
+     * @Author Cool
+     * @Date 17:56 2024/11/7
+     * 滑动窗口
+     **/
+    public int numberOfSubarrays(int[] nums, int k) {
+        int left = 0;
+        int right = 0;
+        int count = 0;
+        int res = 0;
+        while (right < nums.length) {
+            count += nums[right++] & 1;
+            if (count >= k) {
+                int leftCount = 0;
+                while ((nums[left] & 1) == 0) {
+                    leftCount++;
+                    left++;
+                }
+                int rightCount = 0;
+                while (right < nums.length && (nums[right] & 1) == 0) {
+                    right++;
+                    rightCount++;
+                }
+                res += (rightCount + 1) * (leftCount + 1);
+                count--;
+                left++;
+            }
+        }
+        return res;
+    }
+}