使用javaScript实现散列表的线性探查法

Posted 2020-12-16 等不了

class ValuePair{
    constructor(key,value){
        this.key = key;
        this.value = value;
    }
}
function defaultToString(item){
    if(item == null){
        return ‘null‘;
    }
    if(item == undefined){
        return ‘undefined‘;
    }
    if(typeof item ==‘string‘ || item instanceof String){
        return `${item}`;
    }
    return item.toString();
}

class LinearExploration{
    constructor(toStrFn = defaultToString){
        this.toStrFn = toStrFn;
        this.table = {};
    }
    hashCode(key){
        return this.loseloseHashCode(key);
    }
    loseloseHashCode(key){
        if(typeof key == ‘number‘){
            return key;
        }
        let str = this.toStrFn(key);
        let addr = 0;
        for(let i = 0; i < str.length; i++){
            addr += str.charCodeAt(i);
        }
        return addr;
    }
    put(key,value){
        if(key != null && value != null){
            let position = this.hashCode(key);
            if(this.table[position]==null){
                this.table[position] = new ValuePair(key,value);
                return true;
            }
            //从下一个位置开始
            let index = position+1;
            //寻找空余位置
            while(this.table[index]!=null){
                index++;
            }
            this.table[index] = new ValuePair(key,value);
            return true; 
        }
        return ‘undefine‘;
    }
    get(key){
        let position =this.hashCode(key);
        if(this.table[position].key === key){
            return this.table[position].value;
        }
        let index = position+1;
        while(this.table[index]!=null && this.table[index].key != key){
            index++;
        }
        if(this.table[index] != null && this.table[index].key === key){
            return this.table[index].value;
        }
    }
    remove(key){
        const position = this.hashCode(key);
        if(this.table[position]!=null){
            if(this.table[position].key === key){
                delete this.table[position];
                this.verifyRemoveSideEffect(key,position);
                return true;
            }
            let index = position+1;
            while(this.table[index] != null && this.table[index].key != key){
                index++;
            }
            if(this.table[index] != null && this.table[index].key === key){
                delete this.table[index];
                this.verifyRemoveSideEffect(key,index);
                return true;
            }

        }
        return false;
    }
    verifyRemoveSideEffect(key,removedPosition){
        const hash = this.hash(key);
        let index = removedPosition+1;
        while(this.table[index] != null){
            let posHash = this.hashCode(index);
            if(posHash <= hash || posHash < removedPosition){
                this.table[removedPosition] = this.table[index];
                delete this.table[index];
               removedPosition = index;
            }
            index++;
        }
    }
}