2103. Rings and Rods

There are n rings and each ring is either red, green, or blue. The rings are distributed across ten rods labeled from 0 to 9.

You are given a string rings of length 2n that describes the n rings that are placed onto the rods. Every two characters in rings forms a color-position pair that is used to describe each ring where:

  • The first character of the ith pair denotes the ith ring's color ('R', 'G', 'B').
  • The second character of the ith pair denotes the rod that the ith ring is placed on ('0' to '9').

For example, "R3G2B1" describes n == 3 rings: a red ring placed onto the rod labeled 3, a green ring placed onto the rod labeled 2, and a blue ring placed onto the rod labeled 1.

Return the number of rods that have all three colors of rings on them.

 

Example 1:

Input: rings = "B0B6G0R6R0R6G9"
Output: 1
Explanation: 
- The rod labeled 0 holds 3 rings with all colors: red, green, and blue.
- The rod labeled 6 holds 3 rings, but it only has red and blue.
- The rod labeled 9 holds only a green ring.
Thus, the number of rods with all three colors is 1.

Example 2:

Input: rings = "B0R0G0R9R0B0G0"
Output: 1
Explanation: 
- The rod labeled 0 holds 6 rings with all colors: red, green, and blue.
- The rod labeled 9 holds only a red ring.
Thus, the number of rods with all three colors is 1.

Example 3:

Input: rings = "G4"
Output: 0
Explanation: 
Only one ring is given. Thus, no rods have all three colors.

 

Constraints:

  • rings.length == 2 * n
  • 1 <= n <= 100
  • rings[i] where i is even is either 'R', 'G', or 'B' (0-indexed).
  • rings[i] where i is odd is a digit from '0' to '9' (0-indexed).

2103. Rings and Rods
struct Solution;

impl Solution {
    fn count_points(rings: String) -> i32 {
        let mut rgb = vec![vec![false; 3]; 10];
        let rings: Vec<u8> = rings.bytes().collect();
        let n = rings.len() / 2;
        for i in 0..n {
            let color = match rings[2 * i] {
                b'R' => 0,
                b'G' => 1,
                b'B' => 2,
                _ => panic!(),
            };
            let rod = (rings[2 * i + 1] - b'0') as usize;
            rgb[rod][color] = true;
        }
        let mut res = 0;
        for i in 0..10 {
            if rgb[i][0] && rgb[i][1] && rgb[i][2] {
                res += 1;
            }
        }
        res
    }
}

#[test]
fn test() {
    let rings = "B0B6G0R6R0R6G9".to_string();
    let res = 1;
    assert_eq!(Solution::count_points(rings), res);
    let rings = "B0R0G0R9R0B0G0".to_string();
    let res = 1;
    assert_eq!(Solution::count_points(rings), res);
    let rings = "G4".to_string();
    let res = 0;
    assert_eq!(Solution::count_points(rings), res);
}