leetcode: Add 0784

src/leetcode/0377.combination-sum-iv/Cargo.toml

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+[package]
+name = "lc-0377-combination-sum-iv"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]

src/leetcode/0377.combination-sum-iv/index.md

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+
+# 
+
+[问题描述](../problems/)

src/leetcode/0377.combination-sum-iv/src/main.rs

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+// Copyright (c) 2024 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+// Backtracking
+pub fn combination_sum1(nums: Vec<i32>, target: i32) -> i32 {
+    fn backtracking(
+        nums: &[i32],
+        target: i32,
+        max_level: usize,
+        path: &mut Vec<i32>,
+        res: &mut Vec<Vec<i32>>,
+    ) {
+        println!("target: {target}, res count: {}", res.len());
+        // 终止条件就是 target 不大于 0.
+        if target == 0 {
+            res.push(path.clone());
+        }
+        if target <= 0 || path.len() >= max_level {
+            return;
+        }
+
+        // 遍历所有元素.
+        for &num in nums.iter() {
+            if num <= target && path.len() < max_level {
+                // 访问元素
+                path.push(num);
+
+                // 递归搜索
+                backtracking(nums, target - num, max_level, path, res);
+
+                // 撤销访问
+                path.pop();
+            }
+        }
+    }
+
+    debug_assert!((1..=200).contains(&nums.len()));
+    debug_assert!((1..=1000).contains(&target));
+
+    let mut nums = nums;
+    nums.sort_unstable();
+
+    let max_level: usize = (target / nums[0] + 1) as usize;
+
+    // 保存所有结果.
+    let mut res: Vec<Vec<i32>> = Vec::new();
+    // 保存当前路径.
+    let mut path: Vec<i32> = Vec::new();
+
+    backtracking(&nums, target, max_level, &mut path, &mut res);
+    //println!("res: {res:?}");
+    res.len() as i32
+}
+
+pub fn combination_sum2(nums: Vec<i32>, target: i32) -> i32 {
+    fn backtracking(nums: &[i32], target: i32, path: &mut Vec<i32>, count: &mut i32) {
+        println!("target: {target}, res count: {count}");
+        // 终止条件就是 target 不大于 0.
+        if target == 0 {
+            *count += 1;
+        }
+        if target <= 0 {
+            return;
+        }
+
+        // 遍历所有元素.
+        for &num in nums.iter() {
+            if num <= target {
+                // 访问元素
+                path.push(num);
+
+                // 递归搜索
+                backtracking(nums, target - num, path, count);
+
+                // 撤销访问
+                path.pop();
+            }
+        }
+    }
+
+    debug_assert!((1..=200).contains(&nums.len()));
+    debug_assert!((1..=1000).contains(&target));
+
+    // 保存所有结果.
+    let mut count: i32 = 0;
+    // 保存当前路径.
+    let mut path: Vec<i32> = Vec::new();
+
+    backtracking(&nums, target, &mut path, &mut count);
+    count
+}
+
+pub type SolutionFn = fn(Vec<i32>, i32) -> i32;
+
+fn check_solution(func: SolutionFn) {
+    let nums = vec![1, 2, 3];
+    let target = 4;
+    assert_eq!(func(nums, target), 7);
+
+    let nums = vec![9];
+    let target = 3;
+    assert_eq!(func(nums, target), 0);
+
+    // FIXME(Shaohua): Timeout
+    //let nums = vec![1, 2, 3];
+    //let target = 32;
+    //assert_eq!(func(nums, target), 0);
+
+    //let nums = vec![4, 2, 1];
+    //let target = 32;
+    //assert_eq!(func(nums, target), 0);
+}
+
+fn main() {
+    check_solution(combination_sum1);
+    check_solution(combination_sum2);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{check_solution, combination_sum1};
+
+    #[test]
+    fn test_combination_sum1() {
+        check_solution(combination_sum1);
+    }
+}

src/leetcode/0784.letter-case-permutation/Cargo.toml

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+[package]
+name = "lc-0784-letter-case-permutation"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]

src/leetcode/0784.letter-case-permutation/index.md

@@ -0,0 +1,4 @@
+
+# 
+
+[问题描述](../problems/)

src/leetcode/0784.letter-case-permutation/src/main.rs

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+// Copyright (c) 2024 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+// Backtracking
+pub fn letter_case_permutation1(s: String) -> Vec<String> {
+    fn backtracking(chars: &[char], index: usize, path: &mut Vec<char>, res: &mut Vec<String>) {
+        // 终止条件就是所有字符都已经访问过.
+        if index == chars.len() {
+            res.push(String::from_iter(path.iter()));
+            return;
+        }
+
+        // 访问当前元素.
+        let chr: char = chars[index];
+        // 如果当前字符是数字, 就直接访问下个元素.
+        path.push(chr);
+        backtracking(chars, index + 1, path, res);
+        path.pop();
+
+        // 如果当前字符是字母, 就要处理大写和小写.
+        if chr.is_ascii_alphabetic() {
+            path.push(chr.to_ascii_uppercase());
+            backtracking(chars, index + 1, path, res);
+            path.pop();
+        }
+    }
+
+    let chars: Vec<char> = s.to_ascii_lowercase().chars().collect();
+
+    // 存储所有结果.
+    let mut res: Vec<String> = Vec::new();
+    // 存储当前的路径.
+    let mut path: Vec<char> = Vec::new();
+    backtracking(&chars, 0, &mut path, &mut res);
+    res
+}
+
+pub type SolutionFn = fn(String) -> Vec<String>;
+
+fn check_solution(func: SolutionFn) {
+    let s = "a1b2".to_owned();
+    let expected = vec![
+        "a1b2".to_owned(),
+        "a1B2".to_owned(),
+        "A1b2".to_owned(),
+        "A1B2".to_owned(),
+    ];
+    assert_eq!(func(s), expected);
+
+    let s = "3z4".to_owned();
+    let expected = vec!["3z4".to_owned(), "3Z4".to_owned()];
+    assert_eq!(func(s), expected);
+}
+
+fn main() {
+    check_solution(letter_case_permutation1);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{check_solution, letter_case_permutation1};
+
+    #[test]
+    fn test_letter_case_permutation1() {
+        check_solution(letter_case_permutation1);
+    }
+}