source code of slice function

day03/src/main.rs

@@ -0,0 +1,72 @@
+fn main() {
+    let mut s = String::from("hello world");
+    let word = first_word(&s);
+    let first_word = get_first_word(&s);
+    let re_firstw = re_first_word(&s);
+    let sec_word = second_word(&s);
+    let s1 = "hello world";
+    let word_value = slice_first(s1);
+    println!("{}", word);
+    println!("{}", first_word);
+    println!("{}", re_firstw);
+    println!("{}", sec_word);
+    println!("{}", word_value);
+    s.clear();
+}
+
+fn first_word(s: &String) -> usize {
+    let bytes = s.as_bytes();
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return i;
+        }
+    }
+    s.len()
+}
+
+fn get_first_word(s: &String) -> &str {
+    let bytes = s.as_bytes();
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return &s[..i];
+        }
+    }
+    return s;
+}
+
+fn re_first_word(s: &String) -> &str {
+    let bytes = s.as_bytes();
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return &s[..i];
+        }
+    }
+    &s[..]
+}
+
+fn second_word(s: &String) -> &str {
+    let bytes = s.as_bytes();
+    let mut begin: usize = 0;
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' || item == s[s.len() - 1..].as_bytes()[0] {
+            if begin == 0 {
+                begin = i + 1;
+                continue;
+            } else {
+                let end = if item == b' ' { i } else { i + 1 };
+                return &s[begin..end];
+            }
+        }
+    }
+    &s[..]
+}
+
+fn slice_first(s: &str) -> &str {
+    let bytes = s.as_bytes();
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return &s[..i];
+        }
+    }
+    &s[..]
+}