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#664 - Strange Printer

Hard • View on LeetCode • View on GitHub

String Dynamic Programming

Problem Description

There is a strange printer with the following two special properties:

The printer can only print a sequence of the same character each time.
At each turn, the printer can print new characters starting from and ending at any place and will cover the original existing characters.

Given a string s, return the minimum number of turns the printer needed to print it.

Solution

/**
 * @param {string} s
 * @return {number}
 */
var strangePrinter = function(s) {
  const n = s.length;
  const dp = new Array(n).fill().map(() => new Array(n).fill(0));

  for (let i = n - 1; i >= 0; i--) {
    dp[i][i] = 1;
    for (let j = i + 1; j < n; j++) {
      dp[i][j] = dp[i][j - 1] + 1;
      for (let k = i; k < j; k++) {
        if (s[k] === s[j]) {
          dp[i][j] = Math.min(dp[i][j], dp[i][k] + (k + 1 <= j - 1 ? dp[k + 1][j - 1] : 0));
        }
      }
    }
  }

  return dp[0][n - 1];
};

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