1888. 使二进制字符串字符交替的最少反转次数

src/main.rs

@@ -3,37 +3,60 @@ use std::cmp::min;
 struct Solution;
 mod arr;
 impl Solution {
-    pub fn min_operations(s: String) -> i32 {
-        let (mut cnt_a, mut cnt_b) = (0, 0);
-        let mut cnt = 0;
+    pub fn min_flips(s: String) -> i32 {
+        let mut len = s.len();
+        let (mut even_zero, mut even_one, mut odd_zero, mut odd_one) = (0, 0, 0, 0);
+        //let s = (s.clone() + &s).chars().collect::<Vec<_>>();
+        let mut ans = 1e6 as i32;
+        let mut is_even = true;
+
         for c in s.chars() {
-            if cnt & 1 == 1 {
+            if is_even {
+                is_even = false;
                 if c == '0' {
-                    cnt_a += 1;
+                    even_zero += 1;
                 } else {
-                    cnt_b += 1;
+                    even_one += 1;
+                }
+            } else {
+                is_even = true;
+                if c == '0' {
+                    odd_zero += 1;
+                } else {
+                    odd_one += 1;
+                }
+            }
+        }
+        for c in s.chars() {
+            ans = min(ans, min(odd_zero + even_one, odd_one + even_zero));
+            if len & 1 == 1 {
+                if c == '0' {
+                    odd_zero += 1;
+                } else {
+                    odd_one += 1;
                 }
             } else {
                 if c == '0' {
-                    cnt_b += 1;
+                    even_zero += 1;
                 } else {
-                    cnt_a += 1;
+                    even_one += 1;
                 }
             }
-            cnt += 1;
+            (even_zero, even_one, odd_zero, odd_one) = (odd_zero, odd_one, even_zero, even_one);
+            if c == '0' {
+                odd_zero -= 1;
+            } else {
+                odd_one -= 1;
             }
-        min(cnt_a, cnt_b)
+        }
+        ans
     }
 }
-
+// 111000  o0 1 o1 2 j0 2 j1 1
+// 1110001 o0 1 o1 3 j0 2 j1 1
+// 1110001 o0 2 o1 1 j0 1 j1 3
+// 110001     2    1    1    2
 fn main() {
-    let result = Solution::min_operations("1111".to_string());
+    let result = Solution::min_flips("111000".to_string());
     println!("{:?}", result);
 }
-// [[0,0,0,0,0,0],
-//  [0,0,1,0,0,0],
-//  [0,0,0,0,1,0],
-//  [0,0,0,0,0,0],
-//  [0,0,1,0,0,1],
-//  [0,0,0,0,0,0],
-//  [0,0,0,0,0,0]]