20240803 Finished

src/problem/mod.rs

@@ -193,3 +193,4 @@ mod p66_plus_one;
 mod p172_factorial_trailing_zeroes;
 mod p69_sqrtx;
 mod p50_powx_n;
+mod p149_max_points_on_a_line;

src/problem/p149_max_points_on_a_line.rs

@@ -0,0 +1,92 @@
+/**
+ * [149] Max Points on a Line
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+use std::collections::HashMap;
+
+#[derive(Ord, PartialOrd, Eq, PartialEq, Hash)]
+struct Slope {
+    x: i32,
+    y: i32,
+}
+
+impl Slope {
+    fn new(point1: &Vec<i32>, point2: &Vec<i32>) -> Self {
+        let mut x = point1[0] - point2[0];
+        let mut y = point1[1] - point2[1];
+
+        if x == 0 {
+            y = 1;
+        } else if y == 0 {
+            x = 1;
+        } else {
+            if y < 0 {
+                x = -x;
+                y = -y;
+            }
+
+            let gcd = Self::gcd(x.abs(), y.abs());
+            x /= gcd;
+            y /= gcd;
+        }
+
+        Self {
+            x,
+            y,
+        }
+    }
+
+    fn gcd(a: i32, b: i32) -> i32 {
+        if b > 0 {
+            Self::gcd(b, a % b)
+        } else {
+            a
+        }
+    }
+}
+
+impl Solution {
+    pub fn max_points(points: Vec<Vec<i32>>) -> i32 {
+        let n = points.len();
+        if n <= 2 {
+            return n as i32;
+        }
+
+        let mut result = 0;
+        for i in 0..n {
+            if result > n - i || result > n / 2 {
+                break;
+            }
+            
+            let mut map = HashMap::new();
+            for j in i+1..n {
+                let slope = Slope::new(&points[i], &points[j]);
+                
+                let entry = map.entry(slope).or_insert(0);
+                *entry += 1;
+            }
+            
+            let mut max = 0;
+            for i in map.values() {
+                max = max.max(*i);
+            }
+            
+            result = result.max(max + 1);
+        }
+
+        result as i32
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_149() {}
+}