383.ransom-note

描述

Given two stings ransomNote and magazine, return true if ransomNote can be constructed from magazine and false otherwise.

Each letter in magazine can only be used once in ransomNote.

测试用例

Input: ransomNote = "aa", magazine = "ab"
Output: false

Input: ransomNote = "aa", magazine = "aab"
Output: true

题解

首先收集目标字符串内的字符，再去原字符串内进行映射。

var canConstruct = function(ransomNote, magazine) {
    // 收集ransomNote
    let ransomNote_arr = {}, flag = true;
    for(let i = 0; i < ransomNote.length; i++) {
        ransomNote_arr[ransomNote[i]] = ransomNote_arr[ransomNote[i]] ? ransomNote_arr[ransomNote[i]] + 1 : 1;
    }
    for(let i = 0; i < magazine.length; i++) {
        if(ransomNote_arr[magazine[i]]) {
            ransomNote_arr[magazine[i]]--;
        }
    }
    Object.keys(ransomNote_arr).forEach(c => {
        if(ransomNote_arr[c]) {
            flag = false;
            return;
        }
    });
    return flag;
};

结果

Accepted

126/126 cases passed (104 ms)

Your runtime beats 55.2 % of javascript submissions

Your memory usage beats 49.44 % of javascript submissions (42 MB)