source code

day02/src/main.rs

@@ -0,0 +1,53 @@
+#![allow(unused)]
+fn main() {
+    /*let s = String::from("hello");
+    take_ownership(s);
+    let i = 5;
+    make_copy(i);
+    let s1 = String::from("hello world");
+    let (s2, length) = cal_length(s1);
+    println!("The length of \"{}\" is {}", s2, length);*/
+    /*let s1 = String::from("hello world");
+    let length = cal_length(&s1);
+    println!("The length of \"{}\" is {}", s1, length);*/
+    /*let mut s = String::from("hello");
+    change(&mut s);
+    println!("{}", s);*/
+    let s = String::from("hello world");
+    let first_word = first_word(&s);
+    println!("The first word of \"{}\" is {}", s, first_word);
+}
+
+fn 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 take_ownership(mut some_str: String) {
+    some_str.push_str(" world");
+    println!("{}", some_str);
+}
+
+fn make_copy(mut some_int: i32) {
+    some_int += 1;
+    println!("{}", some_int);
+}
+
+fn cal_length(s: String) -> (String, usize) {
+    let length = s.len();
+    return (s, length);
+}*/
+
+/*fn cal_length(s: &String) -> usize {
+    s.len()
+}
+*/
+
+fn change(some_str: &mut String) {
+    some_str.push_str(" world");
+}