287-Find_Duplicate_Number.html

<html>
    <script>
    /**
 * @param {number[]} nums
 * @return {number}
 */
var findDuplicate = function(nums) {
    
    nums.sort((a,b)=> a-b);
    return findDu(nums[0], nums[nums.length-1]);
    
    function findDu(start, end){
        let mid = (start + end)/2;
        
        let i = 0;
        for(; i < nums.length; i++){//find where to start count
            if(nums[i] >= start){
               break;
            }
        }
        
        let count = 0;
        while(nums[i] <= mid){
            i++;
            count++;
        }
        
        if(start === end && count > 1){
            return start;
        }        
        
        
        if(count > mid-start+1){
            return findDu(start, Math.floor(mid));
        }else{
            return findDu(Math.ceil(mid), end);
        }
    }
    
};
</script>
</html>