Improved task 805.

Author: javadev

README.md

@@ -3078,7 +3078,7 @@ implementation 'com.github.javadev:leetcode-in-java:1.12'
 | 0808 |[Soup Servings](src.save/main/java/g0801_0900/s0808_soup_servings/Solution.java)| Medium | Dynamic_Programming, Math, Probability_and_Statistics | 1 | 96.04
 | 0807 |[Max Increase to Keep City Skyline](src.save/main/java/g0801_0900/s0807_max_increase_to_keep_city_skyline/Solution.java)| Medium | Array, Greedy, Matrix | 2 | 23.49
 | 0806 |[Number of Lines To Write String](src.save/main/java/g0801_0900/s0806_number_of_lines_to_write_string/Solution.java)| Easy | Array, String | 1 | 65.23
-| 0805 |[Split Array With Same Average](src.save/main/java/g0801_0900/s0805_split_array_with_same_average/Solution.java)| Hard | Array, Dynamic_Programming, Math, Bit_Manipulation, Bitmask | 1323 | 22.41
+| 0805 |[Split Array With Same Average](src.save/main/java/g0801_0900/s0805_split_array_with_same_average/Solution.java)| Hard | Array, Dynamic_Programming, Math, Bit_Manipulation, Bitmask | 1 | 100.00
 | 0804 |[Unique Morse Code Words](src.save/main/java/g0801_0900/s0804_unique_morse_code_words/Solution.java)| Easy | Array, String, Hash_Table | 2 | 89.27
 | 0803 |[Bricks Falling When Hit](src.save/main/java/g0801_0900/s0803_bricks_falling_when_hit/Solution.java)| Hard | Array, Matrix, Union_Find | 12 | 94.92
 | 0802 |[Find Eventual Safe States](src.save/main/java/g0801_0900/s0802_find_eventual_safe_states/Solution.java)| Medium | Depth_First_Search, Breadth_First_Search, Graph, Topological_Sort, Graph_Theory_I_Day_9_Standard_Traversal | 7 | 74.93

src.save/main/java/g0801_0900/s0805_split_array_with_same_average/Solution.java

@@ -1,41 +1,41 @@
 package g0801_0900.s0805_split_array_with_same_average;
 
 // #Hard #Array #Dynamic_Programming #Math #Bit_Manipulation #Bitmask
-// #2022_03_23_Time_1323_ms_(22.41%)_Space_42.1_MB_(78.14%)
+// #2022_08_19_Time_1_ms_(100.00%)_Space_41.6_MB_(95.76%)
 
 import java.util.Arrays;
 
 public class Solution {
+    private int[] nums;
+    private int[] sums;
+
     public boolean splitArraySameAverage(int[] nums) {
-        int m = nums.length;
-        int sum = 0;
-        for (int n : nums) {
-            sum += n;
+        int len = nums.length;
+        if (len == 1) {
+            return false;
         }
         Arrays.sort(nums);
-        for (int len = 1; len <= m / 2; len++) {
-            if (sum * len % m == 0 && dfs(nums, sum * len / m, len, 0)) {
+        sums = new int[len + 1];
+        for (int i = 0; i < len; i++) {
+            sums[i + 1] = sums[i] + nums[i];
+        }
+        int sum = sums[len];
+        this.nums = nums;
+        for (int i = 1, stop = len / 2; i <= stop; i++) {
+            if ((sum * i) % len == 0 && findSum(i, len, (sum * i) / len)) {
                 return true;
             }
         }
         return false;
     }
 
-    private boolean dfs(int[] nums, int sum, int len, int idx) {
-        if (len == 0) {
-            return sum == 0;
-        }
-        if (sum < 0 || idx >= nums.length) {
-            return false;
-        }
-        if (nums[idx] > sum / len) {
-            return false;
+    private boolean findSum(int k, int pos, int target) {
+        if (k == 1) {
+            while (nums[--pos] > target) {}
+            return nums[pos] == target;
         }
-        for (int i = idx; i < nums.length; i++) {
-            if (i > idx && nums[i] == nums[i - 1]) {
-                continue;
-            }
-            if (dfs(nums, sum - nums[i], len - 1, i + 1)) {
+        for (int i = pos; sums[i] - sums[i-- - k] >= target; ) {
+            if (sums[k - 1] <= target - nums[i] && findSum(k - 1, i, target - nums[i])) {
                 return true;
             }
         }