Reverse Words in a String

src/s0151_reverse_words_in_a_string.cpp

@@ -0,0 +1,49 @@
+#include "s0151_reverse_words_in_a_string.hpp"
+
+// reverse a substring
+void reverseSubStr(string &s, int begin, int end) {
+  for (; begin < end; ++begin, --end) {
+    auto tmp = s[begin];
+    s[begin] = s[end];
+    s[end] = tmp;
+  }
+}
+
+string Solution::reverseWords(string s) {
+  if (s.length() == 0) {
+    return s;
+  }
+  // remove extra spaces
+  int len = s.length();
+  int slow{0};
+  for (int fast{0}; fast < len; ++fast) {
+    if (s[fast] != ' ') {
+      s[slow++] = s[fast];
+    } else {
+      if (fast == len - 1) {
+        break;
+      } else {
+        if (s[fast + 1] != ' ' && slow != 0) {
+          s[slow++] = ' ';
+        }
+      }
+    }
+  }
+  s.resize(slow);
+  // reverse the whole string
+  len = s.length();
+  reverseSubStr(s, 0, len - 1);
+  // reverse each words
+  for (int begin{0}, end{0}; end < len; ++end) {
+    if (end == len - 1) {
+      reverseSubStr(s, begin, end);
+    } else {
+      if (s[end + 1] == ' ') {
+        reverseSubStr(s, begin, end);
+        begin = end + 2;
+        end = end + 1;
+      }
+    }
+  }
+  return s;
+}