【华为面试题】栈（二）

题目

代码

function getMinElectricBoxes(input_str) {
  const n = input_str.length;
  const powerBoxPositions = [];
  let lastPowerBoxUsed = false;

  for (let i = 0; i < n; i++) {
    if (input_str.charAt(i) === "M") {
      if (
        i - 1 >= 0 &&
        input_str.charAt(i - 1) === "M" &&
        i + 1 < n &&
        input_str.charAt(i + 1) === "M"
      ) {
        return -1;
      }
      if (
        (i - 1 === 0 && input_str.charAt(i - 1) === "M") ||
        (i + 1 === n && input_str.charAt(i - 1) === "M")
      ) {
        return -1;
      }

      const pos_left = Math.max(0, i - 1);
      const pos_right = Math.min(n - 1, i + 1);

      if (powerBoxPositions.length > 0 && !lastPowerBoxUsed) {
        if (powerBoxPositions[powerBoxPositions.length - 1] === pos_left) {
          powerBoxPositions.pop();
          lastPowerBoxUsed = true;
        }
      } else {
        lastPowerBoxUsed = false;
      }
      powerBoxPositions.push(pos_right);
    }
  }

  return powerBoxPositions.length;
}

//测试样例
console.log(getMinElectricBoxes("MIIM"));