Leetcode 926 Flip String to Monotone Increasing

Author: jiajionline

0926_Flip String to Monotone Increasing/FlipStringtoMonotoneIncreasing_Prefix.java

@@ -1 +1,24 @@
-t st
+class Solution {
+ public int minFlipsMonoIncr(String s) {
+ int n = s.length();
+ int[] l = new int[n];
+ int[] r = new int[n];
+ l[0] = s.charAt(0) == '0' ? 0 : 1;
+ r[n-1] = s.charAt(n-1) == '1' ? 0 : 1;
+
+ for(int i=1;i<n;i++) {
+ l[i] = s.charAt(i) == '1' ? l[i-1] + 1 : l[i-1];
+ }
+
+ for(int i=n-2;i>=0;i--) {
+ r[i] = s.charAt(i) == '0' ? r[i+1] + 1 : r[i+1];
+ }
+
+ // the case all 0s or 1s
+ int ans = Math.min(r[0], l[n-1]);
+ for(int i=1;i<n;i++) {
+ ans = Math.min(ans, l[i-1] + r[i]);
+ }
+ return ans;
+ }
+}