add new scripts.

Author: everthis

28-implement-strStr().js

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+/**
+ * @param {string} haystack
+ * @param {string} needle
+ * @return {number}
+ */
+const strStr = function(haystack, needle) {
+  if (needle === "") return 0;
+  for (let i = 0; ; i++) {
+    for (let j = 0; ; j++) {
+      if (j === needle.length) {
+        return i;
+      }
+      if (i + j === haystack.length) return -1;
+      if (haystack.charAt(i + j) !== needle.charAt(j)) {
+        break;
+      }
+    }
+  }
+};

29-divide-two-integers.js

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+/**
+ * @param {number} dividend
+ * @param {number} divisor
+ * @return {number}
+ */
+const divide = function(dividend, divisor) {
+  if (!divisor || (dividend === Number.MIN_SAFE_INTEGER && divisor === -1)) {
+    return Number.MAX_SAFE_INTEGER;
+  }
+  const MAX_INT = Math.pow(2, 31) - 1;
+  if (dividend === -2147483648 && divisor === -1) return MAX_INT;
+
+  const sign = (dividend < 0) ^ (divisor < 0) ? -1 : 1;
+  let dvd = Math.abs(dividend);
+  let dvs = Math.abs(divisor);
+  let res = 0;
+
+  while (dvd >= dvs) {
+    let tmp = dvs;
+    let multiple = 1;
+    while (dvd >= tmp << 1 && tmp << 1 > 0) {
+      tmp <<= 1;
+      multiple <<= 1;
+    }
+    dvd -= tmp;
+    res += multiple;
+  }
+  return sign === 1 ? res : -res;
+};

35-search-insert-position.js

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+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number}
+ */
+const searchInsert = function(nums, target) {
+  for (let i = 0; i < nums.length; i++) {
+    if (nums[i] >= target) {
+      return i;
+    } else {
+      if (i === nums.length - 1) {
+        return i + 1;
+      }
+    }
+  }
+};

46-permutations.js

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+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+function permute(nums) {
+  const list = [];
+  // Arrays.sort(nums); // not necessary
+  backtrack(list, [], nums);
+  return list;
+}
+
+function backtrack(list, tempList, nums) {
+  if (tempList.length == nums.length) {
+    list.push(tempList.slice(0));
+  } else {
+    for (let i = 0; i < nums.length; i++) {
+      if (tempList.includes(nums[i])) continue; // element already exists, skip
+      tempList.push(nums[i]);
+      backtrack(list, tempList, nums);
+      tempList.pop();
+    }
+  }
+}

52-n-queens-II.js

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+/**
+ * @param {number} n
+ * @return {number}
+ */
+const totalNQueens = function(n) {
+  //Keeps track of the # of valid solutions
+  let count = 0;
+
+  //Helps identify valid solutions
+  const done = Math.pow(2, n) - 1;
+
+  //Checks all possible board configurations
+  const innerRecurse = function(ld, col, rd) {
+    //All columns are occupied,
+    //so the solution must be complete
+    if (col === done) {
+      count++;
+      return;
+    }
+
+    //Gets a bit sequence with "1"s
+    //whereever there is an open "slot"
+    let poss = ~(ld | rd | col);
+
+    //Loops as long as there is a valid
+    //place to put another queen.
+    while (poss & done) {
+      let bit = poss & -poss;
+      poss -= bit;
+      innerRecurse((ld | bit) >> 1, col | bit, (rd | bit) << 1);
+    }
+  };
+
+  innerRecurse(0, 0, 0);
+
+  return count;
+};

53-maximum-subarray.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+const maxSubArray = function(nums) {
+  let preSum = nums[0];
+  let maxSum = preSum;
+  for (let i = 1; i < nums.length; i++) {
+    preSum = preSum > 0 ? preSum + nums[i] : nums[i];
+    maxSum = Math.max(preSum, maxSum);
+  }
+  return maxSum;
+};

65-valid-number.js

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+/**
+ * @param {string} str
+ * @returns {boolean}
+ */
+const isNumber = function(str) {
+  let i = 0;
+  let s = str;
+  // 跳过前导空格
+  for (; i < s.length && " " == s[i]; ++i);
+  // 处理正负号
+  if ("+" == s[i] || "-" == s[i]) ++i;
+  // 处理后面数字部分
+  let digit = false,
+    dot = false,
+    exp = false;
+  for (; i < s.length; ++i) {
+    if ("." == s[i] && !dot)
+      // '.'不能出现2次，'.'前面可以没有数字
+      dot = true;
+    else if ("e" == s[i] && !exp && digit) {
+      // 'e'不能出现2次，'e'前面必须有数字
+      // 'e'后面不能出现'.'，'e'后面必须是整数（可以是正的或负的）
+      dot = exp = true;
+      if (i + 1 < s.length && ("+" == s[i + 1] || "-" == s[i + 1])) ++i;
+      if (i + 1 >= s.length || !(s[i + 1] >= "0" && s[i + 1] <= "9"))
+        return false;
+    } else if (s[i] >= "0" && s[i] <= "9") digit = true;
+    else break;
+  }
+
+  // 跳过后面空格
+  for (; i < s.length && " " == s[i]; ++i);
+
+  return digit && i == s.length;
+};

68-text-justification.js

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+/**
+ * @param {string[]} words
+ * @param {number} L
+ * @returns {string[]}
+ */
+const fullJustify = function(words, L) {
+  const res = [""];
+  if (words.length === 0 || L === 0) {
+    return res;
+  } else {
+    res.shift();
+    for (let i = 0, k, l; i < words.length; i += k) {
+      for (
+        k = l = 0;
+        i + k < words.length && l + words[i + k].length <= L - k;
+        k++
+      ) {
+        l += words[i + k].length;
+      }
+      let tmp = words[i];
+      for (j = 0; j < k - 1; j++) {
+        if (i + k >= words.length) {
+          tmp += " ";
+        } else {
+          // for (i = 0; i < ((L - l) / (k - 1) + (j < (L - l) % (k - 1))) - 1; i++) {
+          //     tmp += ' ';
+          // }
+          tmp += Array(
+            parseInt((L - l) / (k - 1) + (j < (L - l) % (k - 1))) + 1
+          ).join(" ");
+        }
+        // tmp += (L - l) / (k - 1) + (j < (L - l) % (k - 1)) + ' ';
+        tmp += words[i + j + 1];
+      }
+      // for (i = 0; i < (L - tmp.length); i++) {
+      //     tmp += ' '
+      // }
+      tmp += Array(parseInt(L - tmp.length) + 1).join(" ");
+      // tmp += L - tmp.length + ' ';
+      res.push(tmp);
+    }
+    return res;
+  }
+};

69-sqrt(x).js

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+/**
+ * @param {number} x
+ * @return {number}
+ */
+const mySqrt = function(x) {
+  r = x;
+  while (r * r > x) r = ((r + x / r) / 2) | 0;
+  return r;
+};