Merge pull request #1873 from AkifhanIlgaz/0169

Create: 0169-majority-element.rs

Author: tahsintunan

rust/0169-majority-element.rs

@@ -0,0 +1,48 @@
+use std::collections::HashMap;
+
+impl Solution {
+    // Time Complexity: O(n)
+    // Space Complexity: O(1)
+    // Boyer - Moore Algorithm
+    pub fn majority_element(nums: Vec<i32>) -> i32 {
+        let (mut res, mut count) = (0, 0);
+
+        for n in nums {
+            if count == 0 {
+                res = n;
+            }
+            count += if n == res { 1 } else { -1 };
+        }
+        res
+    }
+
+    // Time Complexity: O(n)
+    // Space Complexity: O(n)
+    // Hashmap
+    pub fn majority_element_2(nums: Vec<i32>) -> i32 {
+        let mut count = HashMap::new();
+
+        let (mut res, mut max_count) = (0, 0);
+
+        for num in nums {
+            *count.entry(num).or_insert(0) += 1;
+            res = if *count.get(&num).unwrap() > max_count {
+                num
+            } else {
+                res
+            };
+            max_count = i32::max(*count.get(&num).unwrap(), max_count);
+        }
+        res
+    }
+
+    // Time Complexity: O(nlogn)
+    // Space Complexity: O(1)
+    // Sorting
+    pub fn majority_element_3(nums: Vec<i32>) -> i32 {
+        // Since we are assured that there will be a majority element which occurs more than nums.len() / 2 times, majority element will be at nums.len() / 2 index
+        let mut nums = nums;
+        nums.sort();
+        nums[nums.len() / 2]
+    }
+}