LeetCode - Algorithms - 344. Reverse String

这题确实easy,做这题倒真可以脱离IDE在leetcode编辑器里刷题了。
做这题，又犯了一次java与js字符串的小错误，在Java里获取String长度的length()是method，在js里获取字符串长度的length是property，老是搞混淆了。

Javascript

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/**
 * @param {string} s
 * @return {string}
 */
var reverseString = function(s) {
    var r = "";
    if (s!=null && s.length>0) {
        for(var i=s.length-1;i>=0;i--) {
            r+=s[i];
        }        
    }
    return r;
};

Submission Detail

  • 476 / 476 test cases passed.
  • Your runtime beats 96.31 % of javascript submissions.

Java

LOOP+SB

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class Solution {
    public String reverseString(String s) {
        StringBuilder sb = new StringBuilder();
        if (s!=null && !s.isEmpty()) {
            for(int i=s.length()-1;i>=0;i--) {
                sb.append(s.charAt(i));
            }
        }
        return sb.toString();
    }
}

Submission Detail

  • 476 / 476 test cases passed.
  • Your runtime beats 13.87 % of java submissions.

跟js写法差不多，这java代码的性能倒不行

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class Solution {
    public String reverseString(String s) {
        StringBuilder sb = new StringBuilder();
        if (s!=null && !s.isEmpty()) {
        	char[] arr = s.toCharArray();
            for(int i=arr.length-1;i>=0;i--) {
                sb.append(arr[i]);
            }
        }
        return sb.toString();
    }
}

Submission Detail

  • 476 / 476 test cases passed.
  • Your runtime beats 5.40 % of java submissions.

SB

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class Solution {
    public String reverseString(String s) {
        String r = "";
        if (s!=null && !s.isEmpty()) {
        	StringBuilder sb = new StringBuilder(s);
        	r = sb.reverse().toString();
        }
        return r;        
    }
}

Submission Detail

  • 476 / 476 test cases passed.
  • Your runtime beats 5.40 % of java submissions.

直接用StringBuilder的reverse()，用StringBuffer好像也类似，性能没什么变化

逆转字符数组

Ref

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class Solution {
    public String reverseString(String s) {
    	String r = "";
        if (s!=null && !s.isEmpty()) {
        	char[] arr = s.toCharArray();
            for (int i=0; i<arr.length/2; i++) {
                char temp = arr[i];
                arr[i] = arr[arr.length-1-i];
                arr[arr.length-1-i] = temp;
            }
            r = new String(arr);
        }
        return r;        
    }
}

Submission Detail

  • 476 / 476 test cases passed.
  • Your runtime beats 7.62 % of java submissions.

Rust

Rust 95%+

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impl Solution {
    pub fn reverse_string(s: &mut Vec<char>) {
        let len = s.len();
        if len > 0 {
            let mut midpoint = len / 2;
            if len % 2 != 0 {
                midpoint += 1;
            }
            for i in 0..midpoint {
                let j = len - i - 1;
                let buffer = s[i];
                s[i] = s[j];
                s[j] = buffer;
            }
        }
    }
}

Submission Detail

  • 478 / 478 test cases passed.
  • Runtime: 20 ms, faster than 95.94% of Rust online submissions for Reverse String.
  • Memory Usage: 5.1 MB, less than 100.00% of Rust online submissions for Reverse String.