solve #151

Author: aylei

src/lib.rs

@@ -145,3 +145,4 @@ mod n0147_insertion_sort_list;
 mod n0148_sort_list;
 mod n0149_max_points_on_a_line;
 mod n0150_evaluate_reverse_polish_notation;
+mod n0151_reverse_words_in_a_string;

src/n0151_reverse_words_in_a_string.rs

@@ -0,0 +1,84 @@
+/**
+ * [151] Reverse Words in a String
+ *
+ * Given an input string, reverse the string word by word.
+ * 
+ *  
+ * 
+ * Example 1:
+ * 
+ * 
+ * Input: "the sky is blue"
+ * Output: "blue is sky the"
+ * 
+ * 
+ * Example 2:
+ * 
+ * 
+ * Input: "  hello world!  "
+ * Output: "world! hello"
+ * Explanation: Your reversed string should not contain leading or trailing spaces.
+ * 
+ * 
+ * Example 3:
+ * 
+ * 
+ * Input: "a good   example"
+ * Output: "example good a"
+ * Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.
+ * 
+ * 
+ *  
+ * 
+ * Note:
+ * 
+ * 
+ * 	A word is defined as a sequence of non-space characters.
+ * 	Input string may contain leading or trailing spaces. However, your reversed string should not contain leading or trailing spaces.
+ * 	You need to reduce multiple spaces between two words to a single space in the reversed string.
+ * 
+ * 
+ *  
+ * 
+ * Follow up:
+ * 
+ * For C programmers, try to solve it in-place in O(1) extra space.
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn reverse_words(mut s: String) -> String {
+        let mut seq = s.trim().chars().collect::<Vec<_>>();
+        seq.reverse();
+        let mut start_idx = 0_usize;
+        let mut i = 0_usize;
+        while i < seq.len() {
+            if seq[i] == ' ' {
+                if i == start_idx {
+                    seq.remove(i);
+                    continue;
+                }
+                seq[start_idx..i].reverse();
+                start_idx = i + 1;
+            }
+            i += 1;
+        }
+        seq[start_idx..].reverse();
+        seq.into_iter().collect()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_151() {
+        assert_eq!(Solution::reverse_words("the sky is blue".to_owned()), "blue is sky the".to_owned());
+        assert_eq!(Solution::reverse_words("  hello world!  ".to_owned()), "world! hello".to_owned());
+    }
+}