696. Count Binary Substrings: AC

Author: tan-wei

src/solution/mod.rs

@@ -505,3 +505,4 @@ mod s0691_stickers_to_spell_word;
 mod s0692_top_k_frequent_words;
 mod s0693_binary_number_with_alternating_bits;
 mod s0695_max_area_of_island;
+mod s0696_count_binary_substrings;

src/solution/s0696_count_binary_substrings.rs

@@ -0,0 +1,74 @@
+/**
+ * [0696] Count Binary Substrings
+ *
+ * Give a binary string s, return the number of non-empty substrings that have the same number of 0's and 1's, and all the 0's and all the 1's in these substrings are grouped consecutively.
+ * Substrings that occur multiple times are counted the number of times they occur.
+ *  
+ * Example 1:
+ *
+ * Input: s = "00110011"
+ * Output: 6
+ * Explanation: There are 6 substrings that have equal number of consecutive 1's and 0's: "0011", "01", "1100", "10", "0011", and "01".
+ * Notice that some of these substrings repeat and are counted the number of times they occur.
+ * Also, "00110011" is not a valid substring because all the 0's (and 1's) are not grouped together.
+ *
+ * Example 2:
+ *
+ * Input: s = "10101"
+ * Output: 4
+ * Explanation: There are 4 substrings: "10", "01", "10", "01" that have equal number of consecutive 1's and 0's.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= s.length <= 10^5
+ * 	s[i] is either '0' or '1'.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/count-binary-substrings/
+// discuss: https://leetcode.com/problems/count-binary-substrings/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn count_binary_substrings(s: String) -> i32 {
+        s.as_bytes()
+            .windows(2)
+            .fold(vec![1], |mut v, w| {
+                if w[0] == w[1] {
+                    *v.last_mut().unwrap() += 1;
+                } else {
+                    v.push(1);
+                }
+                v
+            })
+            .windows(2)
+            .map(|w| w[0].min(w[1]))
+            .sum()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_0696_example_1() {
+        let s = "00110011".to_string();
+        let result = 6;
+
+        assert_eq!(Solution::count_binary_substrings(s), result);
+    }
+
+    #[test]
+    fn test_0696_example_2() {
+        let s = "10101".to_string();
+        let result = 4;
+
+        assert_eq!(Solution::count_binary_substrings(s), result);
+    }
+}