1664. Ways to Make a Fair Array: AC

Author: tan-wei

src/solution/mod.rs

@@ -1254,3 +1254,4 @@ mod s1658_minimum_operations_to_reduce_x_to_zero;
 mod s1659_maximize_grid_happiness;
 mod s1662_check_if_two_string_arrays_are_equivalent;
 mod s1663_smallest_string_with_a_given_numeric_value;
+mod s1664_ways_to_make_a_fair_array;

src/solution/s1664_ways_to_make_a_fair_array.rs

@@ -0,0 +1,119 @@
+/**
+ * [1664] Ways to Make a Fair Array
+ *
+ * You are given an integer array nums. You can choose exactly one index (0-indexed) and remove the element. Notice that the index of the elements may change after the removal.
+ * For example, if nums = [6,1,7,4,1]:
+ *
+ * 	Choosing to remove index 1 results in nums = [6,7,4,1].
+ * 	Choosing to remove index 2 results in nums = [6,1,4,1].
+ * 	Choosing to remove index 4 results in nums = [6,1,7,4].
+ *
+ * An array is fair if the sum of the odd-indexed values equals the sum of the even-indexed values.
+ * Return the number of indices that you could choose such that after the removal, nums is fair.
+ *  
+ * Example 1:
+ *
+ * Input: nums = [2,1,6,4]
+ * Output: 1
+ * Explanation:
+ * Remove index 0: [1,6,4] -> Even sum: 1 + 4 = 5. Odd sum: 6. Not fair.
+ * Remove index 1: [2,6,4] -> Even sum: 2 + 4 = 6. Odd sum: 6. Fair.
+ * Remove index 2: [2,1,4] -> Even sum: 2 + 4 = 6. Odd sum: 1. Not fair.
+ * Remove index 3: [2,1,6] -> Even sum: 2 + 6 = 8. Odd sum: 1. Not fair.
+ * There is 1 index that you can remove to make nums fair.
+ *
+ * Example 2:
+ *
+ * Input: nums = [1,1,1]
+ * Output: 3
+ * Explanation: You can remove any index and the remaining array is fair.
+ *
+ * Example 3:
+ *
+ * Input: nums = [1,2,3]
+ * Output: 0
+ * Explanation: You cannot make a fair array after removing any index.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= nums.length <= 10^5
+ * 	1 <= nums[i] <= 10^4
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/ways-to-make-a-fair-array/
+// discuss: https://leetcode.com/problems/ways-to-make-a-fair-array/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn ways_to_make_fair(nums: Vec<i32>) -> i32 {
+        let n = nums.len();
+        let mut odds = vec![0; n + 1];
+        let mut evens = vec![0; n + 1];
+
+        for i in 0..n {
+            if i % 2 == 0 {
+                odds[i + 1] = odds[i];
+                evens[i + 1] = nums[i] + evens[i];
+            } else {
+                odds[i + 1] = nums[i] + odds[i];
+                evens[i + 1] = evens[i];
+            }
+        }
+
+        let mut result = 0;
+
+        for i in 0..n {
+            let ov = odds[i] - odds[0] + evens[n] - evens[i];
+            let ev = evens[i] - evens[0] + odds[n] - odds[i];
+            if i % 2 == 0 {
+                if ov - nums[i] == ev {
+                    result += 1;
+                }
+            } else {
+                if ov == ev - nums[i] {
+                    result += 1;
+                }
+            }
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1664_example_1() {
+        let nums = vec![2, 1, 6, 4];
+
+        let result = 1;
+
+        assert_eq!(Solution::ways_to_make_fair(nums), result);
+    }
+
+    #[test]
+    fn test_1664_example_2() {
+        let nums = vec![1, 1, 1];
+
+        let result = 3;
+
+        assert_eq!(Solution::ways_to_make_fair(nums), result);
+    }
+
+    #[test]
+    fn test_1664_example_3() {
+        let nums = vec![1, 2, 3];
+
+        let result = 0;
+
+        assert_eq!(Solution::ways_to_make_fair(nums), result);
+    }
+}