README_EN.md

383. Ransom Note

中文文档

Description

Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false.

Each letter in the magazine string can only be used once in your ransom note.

 

Example 1:

Input: ransomNote = "a", magazine = "b"
Output: false

Example 2:

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

Example 3:

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

 

Constraints:

• You may assume that both strings contain only lowercase letters.

Solutions

Python3

class Solution:
    def canConstruct(self, ransomNote: str, magazine: str) -> bool:
        chars = {}
        for i in magazine:
            chars[i] = chars.get(i, 0) + 1
        for i in ransomNote:
            if not chars.get(i):
                return False
            chars[i] -= 1
        return True

Java

class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        int[] chars = new int[26];
        for (int i = 0, n = magazine.length(); i < n; ++i) {
            int idx = magazine.charAt(i) - 'a';
            ++chars[idx];
        }
        for (int i = 0, n = ransomNote.length(); i < n; ++i) {
            int idx = ransomNote.charAt(i) - 'a';
            if (chars[idx] == 0) return false;
            --chars[idx];
        }
        return true;
    }
}

TypeScript

function canConstruct(ransomNote: string, magazine: string): boolean {
    let counter = new Array(26).fill(0);
    let base = 'a'.charCodeAt(0);
    for (let s of magazine) {
        ++counter[s.charCodeAt(0) - base];
    }
    for (let s of ransomNote) {
        let idx = s.charCodeAt(0) - base;
        if (counter[idx] == 0) return false;
        --counter[idx];
    }
    return true;
};

Go

func canConstruct(ransomNote string, magazine string) bool {
	rc := make([]int, 26)
	for _, b := range ransomNote {
		rc[b-'a']++
	}

	mc := make([]int, 26)
	for _, b := range magazine {
		mc[b-'a']++
	}

	for i := 0; i < 26; i++ {
		if rc[i] > mc[i] {
			return false
		}
	}
	return true
}

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