0127-word-ladder.ts

functionladderLength(
beginWord: string,
endWord: string,
wordList: string[]
): number{
if(!wordList.includes(endWord)){
return0;
}
letpatternMap={};
wordList.push(beginWord);

for(letwordofwordList){
for(letx=0;x<word.length;x++){
constpattern=word.slice(0,x)+'*'+word.slice(x+1);
patternMap[pattern]=patternMap[pattern]||[];
patternMap[pattern].push(word);
}
}

letwordCount=1,
queue=[beginWord],
visited=[beginWord];
while(queue.length){
constlevelSize=queue.length;
for(letx=0;x<levelSize;x++){
constword=queue.shift();
if(word===endWord){
returnwordCount;
}

for(letx=0;x<word.length;x++){
constpattern=word.slice(0,x)+'*'+word.slice(x+1);
for(letneiofpatternMap[pattern]){
if(neiinvisited){
continue;
}
visited[nei]=nei;
queue.push(nei);
}
}
}
wordCount++;
}
return0;
}