add 43 modified 32

Author: leopsidom

32.longest-valid-parentheses.rs

@@ -5,9 +5,53 @@
  */
 
 // @lc code=start
+use std::cmp;
+
 impl Solution {
     pub fn longest_valid_parentheses(s: String) -> i32 {
+        let mut chars: Vec<char> = s.chars().collect();
+
+        let left2right = Self::longest_valid_parentheses_one_direction(&chars);
 
+        let mut charsMirror = vec![];
+        chars.reverse();
+        for ch in chars {
+            if ch == '(' {
+                charsMirror.push(')');
+            } else {
+                charsMirror.push('(');
+            }
+        }
+
+        let right2left = Self::longest_valid_parentheses_one_direction(&charsMirror);
+        
+        cmp::max(left2right, right2left)
+    }
+
+    pub fn longest_valid_parentheses_one_direction(chars: &Vec<char>) -> i32 {
+        let N = chars.len();
+        if N <= 1 { return 0; }
+
+        let mut balance = 0;
+        let mut ans = 0;
+        let mut start: i32 = -1;
+
+        for i in 0..N {
+            if chars[i] == '(' {
+                balance += 1;
+            } else {
+                balance -= 1;
+            }
+
+            if balance < 0 {
+                start = i as i32;
+                balance = 0; 
+            } else if balance == 0 {
+                ans = cmp::max(ans, i as i32 - start);
+            }
+        }
+
+        ans
     }
 }
 // @lc code=end

43.multiply-strings.rs

@@ -0,0 +1,53 @@
+/*
+ * @lc app=leetcode id=43 lang=rust
+ *
+ * [43] Multiply Strings
+ */
+
+// @lc code=start
+use std::char;
+
+impl Solution {
+    pub fn multiply(num1: String, num2: String) -> String {
+        let num1chars: Vec<char> = num1.chars().collect();
+        let num2chars: Vec<char> = num2.chars().collect();
+
+        let N1 = num1.len();
+        let N2 = num2.len();
+
+        let mut ans: Vec<u32> = vec![0; N1 + N2];
+
+        for i in 0..N1 {
+            for j in 0..N2 {
+                let x1 = num1chars[i].to_digit(10).unwrap_or(0);
+                let x2 = num2chars[j].to_digit(10).unwrap_or(0);
+                Self::add_num(&mut ans, x1 * x2, N1 - i + N2 - j - 2);
+            }
+        }
+
+        let mut s = String::new();
+
+        for num in ans {
+            s.push(char::from_digit(num, 10).unwrap_or('0'));
+        }
+
+        let ans = s.trim_left_matches('0').to_string();
+        if ans == "" { "0".to_string() } else { ans }
+    }
+
+    pub fn add_num(ans: &mut Vec<u32>, mut num: u32, shift: usize) {
+        let N = ans.len();
+        let mut idx = N - shift - 1;
+        let mut carry = 0;
+
+        while (idx >= 0 && num > 0) || carry > 0 {
+            let sum = ans[idx] + num % 10 + carry;
+            ans[idx] = sum % 10;
+            carry = sum / 10;
+            num /= 10;
+            idx -= 1;
+        }
+    }
+}
+// @lc code=end
+