3739. 统计主要元素子数组数目 II

src/main.rs

@@ -1,51 +1,34 @@
-use crate::arr::make_matrix;
-
 mod arr;
 struct Solution {}
 impl Solution {
-    pub fn restore_ip_addresses(s: String) -> Vec<String> {
-        let s = s
-            .chars()
-            .map(|c| (c as u8 - '0' as u8) as i32)
-            .collect::<Vec<_>>();
-        return Self::dfs(&s, 0, [-1; 4], 0);
-    }
-    fn dfs(s: &Vec<i32>, cur: usize, mut cur_arr: [i32; 4], cur_st: usize) -> Vec<String> {
-        if s.len() - cur < 4 - cur_st - if cur_arr[cur_st] == -1 { 0 } else { 1 }
-            || ((4 - cur_st) * 3 - if cur_arr[cur_st] == -1 {0} else {cur_arr[cur_st].to_string().len()} < s.len() - cur)
-        {
-            return vec![];
+    pub fn count_majority_subarrays(nums: Vec<i32>, target: i32) -> i64 {
+        let mut arr: Vec<i32> = vec![0; nums.len() + 1];
+        for i in 0..nums.len() {
+            arr[i + 1] = arr[i] + if nums[i] == target { 1 } else { -1 };
         }
-        if cur >= s.len()
-        {
-            return vec![cur_arr.map(|t| t.to_string()).join(".")];
-        }
-        if cur_arr[cur_st] == -1 {
-            cur_arr[cur_st] = s[cur];
-            return Self::dfs(s, cur + 1, cur_arr, cur_st);
-        }
-        if cur_arr[cur_st] * 10 + s[cur] <= 255 && cur_arr[cur_st] != 0 {
-            cur_arr[cur_st] = cur_arr[cur_st] * 10 + s[cur];
-            let mut arr = Self::dfs(s, cur + 1, cur_arr, cur_st);
-            if cur_st < 3 {
-                cur_arr[cur_st] /= 10;
-                cur_arr[cur_st + 1] = s[cur];
-                for t in Self::dfs(s,cur + 1, cur_arr, cur_st + 1) {
-                    arr.push(t);
-                }
+        // [-n, n] -> [0, 2n]
+        let n = nums.len() as i32;
+        let mut pre = vec![0; nums.len() * 2 + 1];
+        let mut presum = 0;
+        let mut ans = 0;
+        println!("{:?}", arr);
+        for r in 0..nums.len() {
+            pre[(arr[r] + n) as usize] += 1;
+            if arr[r + 1] > arr[r] {
+                presum += pre[(arr[r] + n) as usize];
+            } else {
+                presum = (presum - pre[(arr[r + 1] + n) as usize]).max(0);
             }
-            return arr;
+            ans += presum;
         }
-        if cur_st < 3{
-            cur_arr[cur_st + 1] = s[cur];
-            return Self::dfs(s, cur + 1, cur_arr, cur_st + 1);
-        }
-        vec![]
+        ans
     }
 }
 fn main() {
+    //    1   2   2   3
+    //  0  -1   0   1   0
     println!(
         "{:?}",
-        Solution::restore_ip_addresses("0000".to_string())
+        Solution::count_majority_subarrays(vec![1, 2, 2, 3], 2)
     );
 }