leetCode/387.字符串中的第一个唯一字符.html

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    <title>387. 字符串中的第一个唯一字符</title>
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    <script>
      // https://leetcode-cn.com/problems/first-unique-character-in-a-string/

      // 给定一个字符串 s ，找到 它的第一个不重复的字符，并返回它的索引 。如果不存在，则返回 -1 。
      // 提示：
      // 1 <= s.length <= 105
      // s 只包含小写字母

      /**
       * @param {string} s
       * @return {number}
       */
      var firstUniqChar = function (s) {};

      // --- answer-1 ---

      // 先进行一次字符统计
      var firstUniqChar = function (s = '') {
        let map = {};
        for (let i = 0; i < s.length; i++) {
          map[s[i]] = (map[s[i]] || 0) + 1;
        }
        for (let i = 0; i < s.length; i++) {
          if (map[s[i]] === 1) return i;
        }
        return -1;
      };

      // --- answer-1 ---

      // --- answer-2 ---

      // 队列 + hash
      var firstUniqChar = function (s) {
        const position = new Map();
        const q = [];
        const n = s.length;
        for (let [i, ch] of Array.from(s).entries()) {
          if (!position.has(ch)) {
            position.set(ch, i);
            q.push([s[i], i]);
          } else {
            position.set(ch, -1);
            while (q.length && position.get(q[0][0]) === -1) {
              q.shift();
            }
          }
        }
        return q.length ? q[0][1] : -1;
      };

      // --- answer-2 ---

      var s = 'leetcode';
      var result = 0;

      var s = 'loveleetcode';
      var result = 2;

      var s = 'aabb';
      var result = -1;

      console.log('s = ', s);
      console.log('result = ', result);
      console.log('firstUniqChar = ', firstUniqChar(s));
    </script>
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