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467 lines
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<main>
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<h1 id="flow-control"><a class="header" href="#flow-control">Flow control</a></h1>
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<h3 id="ifelse"><a class="header" href="#ifelse">If/else</a></h3>
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<ol>
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<li>🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill in the blanks
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fn main() {
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let n = 5;
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if n < 0 {
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println!("{} is negative", n);
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} __ n > 0 {
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println!("{} is positive", n);
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} __ {
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println!("{} is zero", n);
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}
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} </code></pre></pre>
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<ol start="2">
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<li>🌟🌟 <code>If/else</code> expression can be used in assignments.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fix the errors
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fn main() {
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let n = 5;
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let big_n =
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if n < 10 && n > -10 {
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println!(", and is a small number, increase ten-fold");
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10 * n
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} else {
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println!(", and is a big number, halve the number");
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n / 2.0 ;
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}
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println!("{} -> {}", n, big_n);
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} </code></pre></pre>
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<h3 id="for"><a class="header" href="#for">For</a></h3>
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<ol start="3">
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<li>🌟 The <code>for in</code> construct can be used to iterate through an Iterator, e.g a range <code>a..b</code>.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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fn main() {
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for n in 1..=100 { // modify this line to make the code work
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if n == 100 {
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panic!("NEVER LET THIS RUN")
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}
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}
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println!("Success!");
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} </code></pre></pre>
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<ol start="4">
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<li>🌟🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fix the errors without adding or removing lines
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fn main() {
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let names = [String::from("liming"),String::from("hanmeimei")];
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for name in names {
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// Do something with name...
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}
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println!("{:?}", names);
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let numbers = [1, 2, 3];
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// The elements in numbers are Copy，so there is no move here
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for n in numbers {
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// Do something with n...
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}
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println!("{:?}", numbers);
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} </code></pre></pre>
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<ol start="5">
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<li>🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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let a = [4, 3, 2, 1];
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// Iterate the indexing and value in 'a'
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for (i,v) in a.__ {
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println!("The {}th element is {}",i+1,v);
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}
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}</code></pre></pre>
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<h3 id="while"><a class="header" href="#while">While</a></h3>
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<ol start="6">
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<li>🌟🌟 The <code>while</code> keyword can be used to run a loop when a condition is true.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill in the blanks to make the last println! work !
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fn main() {
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// A counter variable
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let mut n = 1;
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// Loop while the condition is true
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while n __ 10 {
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if n % 15 == 0 {
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println!("fizzbuzz");
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} else if n % 3 == 0 {
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println!("fizz");
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} else if n % 5 == 0 {
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println!("buzz");
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} else {
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println!("{}", n);
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}
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__;
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}
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println!("n reached {}, so loop is over",n);
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}</code></pre></pre>
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<h3 id="continue-and-break"><a class="header" href="#continue-and-break">Continue and break</a></h3>
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<ol start="7">
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<li>🌟 Use <code>break</code> to break the loop.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill in the blank
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fn main() {
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let mut n = 0;
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for i in 0..=100 {
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if n == 66 {
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__
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}
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n += 1;
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}
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assert_eq!(n, 66);
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println!("Success!");
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}</code></pre></pre>
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<ol start="8">
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<li>🌟🌟 <code>continue</code> will skip over the remaining code in current iteration and go to the next iteration.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill in the blanks
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fn main() {
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let mut n = 0;
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for i in 0..=100 {
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if n != 66 {
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n+=1;
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__;
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}
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__
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}
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assert_eq!(n, 66);
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println!("Success!");
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}</code></pre></pre>
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<h3 id="loop"><a class="header" href="#loop">Loop</a></h3>
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<ol start="9">
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<li>🌟🌟 Loop is usually used together with <code>break</code> or <code>continue</code>.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill in the blanks
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fn main() {
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let mut count = 0u32;
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println!("Let's count until infinity!");
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// Infinite loop
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loop {
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count += 1;
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if count == 3 {
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println!("three");
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// Skip the rest of this iteration
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__;
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}
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println!("{}", count);
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if count == 5 {
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println!("OK, that's enough");
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__;
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}
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}
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assert_eq!(count, 5);
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println!("Success!");
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}</code></pre></pre>
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<ol start="10">
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<li>🌟🌟 Loop is an expression, so we can use it with <code>break</code> to return a value</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill in the blank
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fn main() {
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let mut counter = 0;
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let result = loop {
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counter += 1;
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if counter == 10 {
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__;
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}
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};
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assert_eq!(result, 20);
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println!("Success!");
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}</code></pre></pre>
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<ol start="11">
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<li>🌟🌟🌟 It's possible to break or continue outer loops when dealing with nested loops. In these cases, the loops must be annotated with some 'label, and the label must be passed to the break/continue statement.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill in the blank
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fn main() {
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let mut count = 0;
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'outer: loop {
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'inner1: loop {
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if count >= 20 {
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// This would break only the inner1 loop
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break 'inner1; // `break` is also works.
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}
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count += 2;
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}
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count += 5;
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'inner2: loop {
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if count >= 30 {
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// This breaks the outer loop
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break 'outer;
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}
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|
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// This will continue the outer loop
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continue 'outer;
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}
|
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}
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|
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assert!(count == __);
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||
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println!("Success!");
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||
}</code></pre></pre>
|
||
<blockquote>
|
||
<p>You can find the solutions <a href="https://github.com/sunface/rust-by-practice">here</a>(under the solutions path), but only use it when you need it</p>
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</blockquote>
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