前端算法之哈字典&希表

一、力扣01两数之和

<script type="text/javascript">
var twoSum = function(nums, target) {
    let map = new Map();
    for( let i=0;i<nums.length;i++){
        num = target - nums[i];
        if( map.has(num) ){
            return [map.get(num),i];
        }
        map.set(nums[i],i);
    }
};
</script>

二、力扣217存在重复元素

<script type="text/javascript">
var containsDuplicate = function(nums) {
//视频教程：https://www.xuexiluxian.cn/course/detail/8429c57c800544f6b49fe73f9aae21de
    // let map = new Map();
    // for(const x of nums ){
    //     if( map.has(x) ){
    //         return true;
    //     }
    //     map.set(x,1);
    // }
    // return false;
    let set = new Set();
    for( const x of nums ){
        if( set.has(x) ){
            return true;
        }
        set.add(x);
    }
    return false;
};
</script>

三、力扣349两个数组的交集

<script type="text/javascript">
//视频教程：https://www.xuexiluxian.cn/course/detail/8429c57c800544f6b49fe73f9aae21de
var intersection = function(nums1, nums2) {
    let set = new Set(nums2);
    return [...new Set(nums1)].filter((val)=>set.has(val));
};
</script>

四、力扣1207独一无二的出现次数

<script type="text/javascript">
function fun( s ){
    let maxNum = 0;
    let maxStr = '';
    let map = new Map();
    for( let item of s ){
        map.set( item , (map.get(item) || 0 ) + 1 )
    }

    for(let [key,value] of map){
        if( value > maxNum ){
            maxStr = key;
            maxNum = value;
        }
    }
    return [maxStr , maxNum];
}
console.log( fun('aaabbbbccccccc') );
</script>

五、力扣03无重复字符的最长子串

<script type="text/javascript">
var lengthOfLongestSubstring = function(s) {
    const map = new Map();
    let l = 0;
    let num = 0;
    for( let i =0;i<s.length;i++){
        if( map.has(s[i]) && map.get(s[i]) >= l ){
            l = map.get(s[i]) + 1;
        }
        num = Math.max( num , i+1-l );
        map.set(s[i],i);
    }
    return num;
};
</script>