solve leetcode |1929|[Concatenation of Array]

Author: pymongo

README.md

@@ -63,7 +63,7 @@ leetcode_solutions
 |50|[Pow(x, n)](https://leetcode.com/problems/powx-n/)|[Rust](src/math/pow.rs)|
 |51|[N Queens](https://leetcode.com/problems/n-queens)|[Python](https://github.com/pymongo/python_leetcode/blob/master/dfs_perm_comb/n_queens.py), [Rust](src/bfs_dfs_backtracking/n_queens.rs)||
 |52|[N Queens II](https://leetcode.com/problems/n-queens-ii)|[Python](https://github.com/pymongo/python_leetcode/blob/master/dfs_perm_comb/n_queens.py), [Rust](src/bfs_dfs_backtracking/n_queens.rs)|
-|53|[Maximum Subarray](https://leetcode.com/problems/maximum-subarray/)|[Python](https://github.com/pymongo/python_leetcode/blob/master/greedy/maximum_subarray.py)|greedy, dp|
+|53|[Maximum Subarray](https://leetcode.com/problems/maximum-subarray/)|[Rust](src/greedy/maximum_subarray.rs)|
 |54|[Spiral Matrix](https://leetcode.com/problems/spiral-matrix/)|[Rust](src/easy/grid_or_matrix/spiral_matrix.rs)|
 |55|[Jump Game](https://leetcode.com/problems/jump-game/)|[Python](https://github.com/pymongo/python_leetcode/blob/master/dp/jump_game.py)|greedy, dp|
 |58|[Length of Last Word](https://leetcode.com/problems/length-of-last-word/)|[Rust](src/easy/leetcode_very_easy)|
@@ -485,6 +485,8 @@ leetcode_solutions
 |1880|[Check if Word Equals...](https://leetcode.com/problems/check-if-word-equals-summation-of-two-words/)|[Rust](src/easy/leetcode_very_easy.rs)|
 |1913|[Maximum Product Diff...](https://leetcode.com/problems/maximum-product-difference-between-two-pairs/)|[Rust](src/easy/leetcode_very_easy.rs)|
 |1920|[Build Array from Permutation](https://leetcode.com/problems/build-array-from-permutation)|[Rust](src/easy/leetcode_very_easy.rs)|
+|1925|[Count Square Sum Triples](https://leetcode.com/problems/count-square-sum-triples/)|[Rust](src/easy/leetcode_very_easy.rs)|
+|1929|[Concatenation of Array](https://leetcode.com/problems/concatenation-of-array/)|[Rust](src/easy/leetcode_very_easy.rs)|
 
 ---
 
@@ -522,7 +524,6 @@ lintcode_problems
 |31|[Partition Array](https://lintcode.com/problem/partition-array/)|[Python](https://github.com/pymongo/python_leetcode/blob/master/partition_array/partition_array.py)|two_pointers|
 |38|[Search a 2D Matrix II](https://lintcode.com/problem/search-a-2d-matrix-ii/)|leetcode_240|
 |40|[Implement Queue by Two Stacks](https://lintcode.com/problem/implement-queue-by-two-stacks/)|[Python](https://github.com/pymongo/python_leetcode/blob/master/collections/impl_queue_by_stack.py)||
-|41|[Maximum Subarray](https://lintcode.com/problem/maximum-subarray/)|[Python](https://github.com/pymongo/python_leetcode/blob/master/greedy/maximum_subarray.py)|greedy, dp|
 |49|[Sort Letters by Case](https://lintcode.com/problem/sort-letters-by-case/)|[Python](https://github.com/pymongo/python_leetcode/blob/master/partition_array/sort_colors.py)|
 |50|[Product of Array Exclude Itself](https://lintcode.com/problem/product-of-array-exclude-itself/)|leetcode_lcof_66|
 |52|[Next Permutation](https://lintcode.com/problem/next-permutation/)|[Python](https://github.com/pymongo/python_leetcode/blob/master/dfs_perm_comb/next_permutation.py)||

src/easy/leetcode_very_easy.rs

@@ -2683,3 +2683,25 @@ fn display_table(orders: Vec<Vec<String>>) -> Vec<Vec<String>> {
     }
     ret
 }
+
+/// https://leetcode.com/problems/count-square-sum-triples/
+fn count_triples(n: i32) -> i32 {
+    let n = f64::from(n * n).sqrt() as i32;
+    let mut ret = 0;
+    for a in 1..=n {
+        for b in a..=n {
+            for c in b..=n {
+                if a * a + b * b == c * c {
+                    ret += 2;
+                }
+            }
+        }
+    }
+    ret
+}
+
+/// https://leetcode.com/problems/concatenation-of-array/
+fn get_concatenation(mut nums: Vec<i32>) -> Vec<i32> {
+    nums.extend(nums.clone());
+    nums
+}

src/greedy/maximum_subarray.rs

@@ -0,0 +1,20 @@
+/*! https://leetcode.com/problems/maximum-subarray/
+53. 最大子序和
+给定一个整数数组 nums ，找到一个具有最大和的连续子数组（子数组最少包含一个元素），返回其最大和
+O(n)的算法：贪心: if cur_sum+nums[i] < nums[i]，则以舍弃前面的元素，从i开始从新算最大长度
+O(n)的算法：动态规划(「滚动数组」): 如果当前元素的前一个元素大于0，则当前元素的值 += 前一个元素的值
+O(logn)的算法?分治?: 求区间内最值用「线段树」，但是加上预处理之后，就跟贪心一样是O(n)，本题没有logn的解法
+这个分治方法类似于「线段树求解 LCIS 问题」的 pushUp 操作
+*/
+
+fn maximum_subarray_dp(mut nums: Vec<i32>) -> i32 {
+    let size = nums.len();
+    let mut max_sum = nums[0];
+    for i in 1..size {
+        if nums[i - 1] > 0 {
+            nums[i] += nums[i - 1];
+        }
+        max_sum = max_sum.max(nums[i]);
+    }
+    max_sum
+}

src/greedy/mod.rs

@@ -17,6 +17,7 @@ mod factorial_trailing_zeroes;
 mod gas_station;
 mod int_to_roman;
 mod majority_element;
+mod maximum_subarray;
 mod partition_labels;
 mod prefix_sum_subarray;
 mod product_of_array_except_self;