TS Solution -- optimal time complexity but not optimised:

function appendAndDelete(s: string, t: string, k: number): string { // Write your code here

for(let i = 0; i < Math.max(s.length, t.length); i++) {

    if(s[i] != t[i]) {

        let numCharsToDelete:number = s.length - i
        let numCharsToRebuild:number = t.length - i
        let minActionsToZeroAndBack:number = (s.length - numCharsToDelete) * 2

        k -= numCharsToDelete + numCharsToRebuild

        if (k >= 0 && (k % 2 === 0 || minActionsToZeroAndBack <= k )) {
            return "Yes"
        } else {
            return "No"
        }
    }
}

return "Yes" 

}