FlipStringToMonotoneIncreasing926.kt

package medium

/**
 * A binary string is monotone increasing if it consists of some number of 0's (possibly none), followed by some number of 1's (also possibly none).

You are given a binary string s. You can flip s[i] changing it from 0 to 1 or from 1 to 0.

Return the minimum number of flips to make s monotone increasing.



Example 1:

Input: s = "00110"
Output: 1
Explanation: We flip the last digit to get 00111.
Example 2:

Input: s = "010110"
Output: 2
Explanation: We flip to get 011111, or alternatively 000111.
Example 3:

Input: s = "00011000"
Output: 2
Explanation: We flip to get 00000000.


Constraints:

1 <= s.length <= 105
s[i] is either '0' or '1'.
 */
fun minFlipsMonoIncr(s: String): Int {
    var res = 0
    var ones = 0

    for (i in s.indices) {
        if (s[i] == '0')
            res++
        else
            ones++
        res = Math.min(res, ones)
    }

    return res
}

fun minFlipsMonoIncrSol2(s: String): Int {
    var zeroToOnes = 0
    var onesCount = 0
    var i = 0
    while (i < s.length && s[i] == '0') {
        i++
    }

    while (i < s.length) {
        if (s[i] == '0') {
            zeroToOnes++
        } else {
            onesCount++
        }
        if (zeroToOnes > onesCount)
            zeroToOnes = onesCount
        i++
    }
    return zeroToOnes
}