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| 1 | +'use strict'; |
| 2 | + |
| 3 | +const fs = require('fs'); |
| 4 | + |
| 5 | +process.stdin.resume(); |
| 6 | +process.stdin.setEncoding('utf-8'); |
| 7 | + |
| 8 | +let inputString = ''; |
| 9 | +let currentLine = 0; |
| 10 | + |
| 11 | +process.stdin.on('data', inputStdin => { |
| 12 | + inputString += inputStdin; |
| 13 | +}); |
| 14 | + |
| 15 | +process.stdin.on('end', _ => { |
| 16 | + inputString = inputString.replace(/\s*$/, '') |
| 17 | + .split('\n') |
| 18 | + .map(str => str.replace(/\s*$/, '')); |
| 19 | + |
| 20 | + main(); |
| 21 | +}); |
| 22 | + |
| 23 | +function readLine() { |
| 24 | + return inputString[currentLine++]; |
| 25 | +} |
| 26 | + |
| 27 | +// Complete the highestValuePalindrome function below. |
| 28 | +const isValidPalindrome = (s) => { |
| 29 | + let m = Math.ceil(s.length / 2); |
| 30 | + for (let i = 0, j = s.length - 1; i < m, j >= m; i++ , j--) { |
| 31 | + if (s[i] !== s[j]) { return false; } |
| 32 | + } |
| 33 | + return true; |
| 34 | +} |
| 35 | +function highestValuePalindrome(s, n, k) { |
| 36 | + let lives = k; |
| 37 | + let mod = new Array(n).fill(false); |
| 38 | + let temp = s.split(''); |
| 39 | + for (let i = 0; i < n / 2; i++) { |
| 40 | + let j = n - i - 1; |
| 41 | + if (temp[i] != temp[j]) { |
| 42 | + mod[i] = true; |
| 43 | + lives--; |
| 44 | + } |
| 45 | + if (temp[i] < temp[j]) |
| 46 | + temp[i] = temp[j]; |
| 47 | + else if (temp[i] > temp[j]) |
| 48 | + temp[j] = temp[i]; |
| 49 | + if (lives < 0) |
| 50 | + return "-1"; |
| 51 | + } |
| 52 | + let j = 0; |
| 53 | + while ((lives > 0) && (j < n / 2)) { |
| 54 | + if (temp[j] != '9') { |
| 55 | + if (mod[j]) |
| 56 | + lives++; |
| 57 | + if (lives > 1) { |
| 58 | + temp[j] = '9'; |
| 59 | + temp[n - j - 1] = '9'; |
| 60 | + lives -= 2; |
| 61 | + } |
| 62 | + } |
| 63 | + j++; |
| 64 | + } |
| 65 | + if (n % 2 == 1) { |
| 66 | + if (lives > 0) |
| 67 | + temp[Math.floor(n / 2)] = '9'; |
| 68 | + } |
| 69 | + return temp.join(''); |
| 70 | +} |
| 71 | + |
| 72 | +function main() { |
| 73 | + const ws = fs.createWriteStream(process.env.OUTPUT_PATH); |
| 74 | + |
| 75 | + const nk = readLine().split(' '); |
| 76 | + |
| 77 | + const n = parseInt(nk[0], 10); |
| 78 | + |
| 79 | + const k = parseInt(nk[1], 10); |
| 80 | + |
| 81 | + const s = readLine(); |
| 82 | + |
| 83 | + let result = highestValuePalindrome(s, n, k); |
| 84 | + |
| 85 | + ws.write(result + "\n"); |
| 86 | + |
| 87 | + ws.end(); |
| 88 | +} |
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