Mình xin giới thiệu lại cách khởi tạo và truy cập phần tử trong mảng.
1. Khởi tạo mảng
Ví dụ ta khởi tạo một mảng ages có 7 phần tử:
1 2 3 | <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> ages <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">int</span><span class="token punctuation">[</span><span class="token number">7</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token keyword">int</span> ages<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">int</span><span class="token punctuation">[</span><span class="token number">7</span><span class="token punctuation">]</span><span class="token punctuation">;</span> |
Gán gía trị cho mỗi phần từ:
1 2 3 4 5 6 7 8 | ages<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">4</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">9</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">5</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">8</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">6</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">7</span><span class="token punctuation">;</span> |
Hoặc gán lúc tạo mảng:
1 2 3 | <span class="token keyword">int</span> ages<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">9</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">}</span><span class="token punctuation">;</span> <span class="token keyword">int</span> ages<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">9</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">}</span><span class="token punctuation">;</span> |
2. Truy cập phần từ bất kỳ
Ví dụ cú pháp:
1 2 | <span class="token keyword">int</span> ages<span class="token punctuation">[</span><span class="token number">7</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">8</span><span class="token punctuation">,</span> <span class="token number">9</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">}</span><span class="token punctuation">;</span> |
1 2 3 | <span class="token keyword">int</span> a <span class="token operator">=</span> ages<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// a = 9</span> <span class="token keyword">int</span> b <span class="token operator">=</span> ages<span class="token punctuation">[</span><span class="token number">5</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// b = 5</span> |
Biến a có giá trị là 9, b có giá trị là 5.
3. Khởi tạo và truy cập mảng hai chiều
Ta khởi tạo mảng hai chiều ages,
với hàng đầu tiên là 4 phần tử, hàng thứ hai là 4 phần tử, hàng thứ ba là 5 phần tử.
Ví dụ cú pháp:
1 2 3 | <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> ages <span class="token operator">=</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token keyword">int</span> ages<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span> |
Khởi tạo hàng đầu tiên:
1 2 3 4 5 6 | ages<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">int</span><span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">]</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">4</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">7</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">9</span><span class="token punctuation">;</span> |
Khởi tạo hàng thứ hai:
1 2 3 4 5 6 | ages<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">int</span><span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">]</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">4</span><span class="token punctuation">;</span> |
Khởi tạo mảng thứ ba:
1 2 3 4 5 6 7 | ages<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">int</span><span class="token punctuation">[</span><span class="token number">5</span><span class="token punctuation">]</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">4</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">7</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">9</span><span class="token punctuation">;</span> ages<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">;</span> |
Về cú pháp truy cập:
1 2 3 4 | <span class="token keyword">int</span> row13 <span class="token operator">=</span> ages<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// row12 = 7</span> <span class="token keyword">int</span> row24 <span class="token operator">=</span> ages<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// row24 = 4</span> <span class="token keyword">int</span> row31 <span class="token operator">=</span> ages<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// row31 = 3</span> |
Có gì mong mọi người góp ý.