find_the_duplicate_number_287.rs

use crate::Solution;
impl Solution {
    pub fn find_duplicate(nums: Vec<i32>) -> i32 {
        let mut slow = nums[0];
        let mut fast = nums[0];

      
        loop {
            slow = nums[slow as usize];
            fast = nums[nums[fast as usize] as usize];

            if slow == fast {
                break; 
            }
        }

        let mut ptr1 = nums[0];
        let mut ptr2 = slow;
        
        while ptr1 != ptr2 {
            ptr1 = nums[ptr1 as usize];
            ptr2 = nums[ptr2 as usize];
        }

        ptr1
    }
}