Improved task

Author: javadev

src/main/java/g3601_3700/s3666_minimum_operations_to_equalize_binary_string/Solution.java

@@ -1,106 +1,44 @@
 package g3601_3700.s3666_minimum_operations_to_equalize_binary_string;
 
-// #Hard #Biweekly_Contest_164 #2025_09_06_Time_4_ms_(100.00%)_Space_46.11_MB_(31.99%)
+// #Hard #Biweekly_Contest_164 #2025_09_06_Time_6_ms_(83.87%)_Space_45.74_MB_(64.52%)
 
 public class Solution {
     public int minOperations(String s, int k) {
-        int zero = 0;
-        for (char chr : s.toCharArray()) {
-            zero += '1' - chr;
-        }
-        if (zero % 2 != 0 && k % 2 == 0) {
-            return -1;
-        }
-        if (zero % k == 0) {
-            return zero / k;
+        int n = s.length();
+        int cnt0 = 0;
+        for (char c : s.toCharArray()) {
+            if (c == '0') {
+                cnt0++;
+            }
         }
-        if (k % 2 == 0) {
-            return get(zero, s.length(), k);
-        } else {
-            return get1(zero, s.length(), k);
+        if (cnt0 == 0) {
+            return 0;
         }
-    }
-
-    private int get(int zero, int sum, int k) {
-        int l = zero;
-        int r = zero;
-        int res = 0;
-        while (true) {
-            if (l == 0) {
-                return res;
-            }
-            int lNext;
-            if (l >= k) {
-                lNext = l - k;
-            } else if (r >= k) {
-                lNext = 0;
-            } else {
-                lNext = k - r;
-            }
-            int rNext;
-            int a = sum - r;
-            int b = sum - l;
-            if (a >= k) {
-                rNext = r + k;
-            } else if (b >= k) {
-                rNext = sum;
-            } else {
-                rNext = l + b - (k - b);
-            }
-            if (l == lNext && r == rNext) {
-                break;
-            }
-            if (l > lNext) {
-                l = lNext;
-            }
-            if (r < rNext) {
-                r = rNext;
-            }
-            res++;
+        if (k == n) {
+            return cnt0 == n ? 1 : -1;
         }
-        return -1;
-    }
-
-    private int get1(int zero, int sum, int k) {
-        int[] l = {Integer.MAX_VALUE, zero};
-        int[] r = {Integer.MIN_VALUE, zero};
-        int res = 0;
-        while (true) {
-            int idx1 = res % 2;
-            int idx = 1 - idx1;
-            int lNext;
-            int offset = 1 - l[idx] % 2;
-            if (l[idx] >= k) {
-                lNext = l[idx] - k;
-            } else if (r[idx] >= k) {
-                lNext = offset;
-            } else {
-                lNext = k - r[idx];
-            }
-            int rNext;
-            int a = sum - r[idx];
-            int b = sum - l[idx];
-            if (a >= k) {
-                rNext = r[idx] + k;
-            } else if (b >= k) {
-                rNext = sum - offset;
-            } else {
-                rNext = l[idx] + b - (k - b);
-            }
-            if (l[idx1] == lNext && r[idx1] == rNext) {
-                break;
-            }
-            if (l[idx1] > lNext) {
-                l[idx1] = lNext;
-            }
-            if (r[idx1] < rNext) {
-                r[idx1] = rNext;
-            }
-            res++;
-            if (l[idx1] == 0) {
-                return res;
+        int kP = k & 1;
+        int needP = cnt0 & 1;
+        long best = Long.MAX_VALUE;
+        for (int p = 0; p <= 1; p++) {
+            if ((p * kP) % 2 != needP) {
+                continue;
+            }
+            long mismatch = (p == 0) ? cnt0 : (n - cnt0);
+            long b1 = (cnt0 + k - 1L) / k;
+            long b2;
+            b2 = (mismatch + (n - k) - 1L) / (n - k);
+            long lb = Math.max(b1, b2);
+            if (lb < 1) {
+                lb = 1;
+            }
+            if ((lb & 1) != p) {
+                lb++;
+            }
+            if (lb < best) {
+                best = lb;
             }
         }
-        return -1;
+        return best == Long.MAX_VALUE ? -1 : (int) best;
     }
 }