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Determines if a character is unique

Example 1:

Input: s = “leet code” Output: false Example 2: Input: s = “ABC” Output: true

Limitations:

< 1 >

0 <= len(s) <= 100

< 2 >

Bonus points if you don’t use extra data structures.

Solution 1 Iterates through the string to determine where a character appears

Memory consumption is 37.5MB

/** * @param {string} astr * @return {Boolean} */ var isUnique = function(astr) // The second indexOf gets the first occurrence of the specified character. i<=astr.length; i++){ //if(astr.indexOf(astr[i], astr.indexOf(astr[i])+1)! For (let I of astr) {if (astr.indexof (I)){if (astr.indexof (I)! == astr.lastIndexOf(i)) { return false } } return true };Copy the code

Solution 2 uses Set in ES6

Set

The Set object allows you to store a unique value of any type, either a primitive value or an object reference.

Special values

  • +0 and -0 are identical in the storage of judgment uniqueness, so they are not repeated;
  • Undefined and undefined are identical, so do not repeat;
  • NaN is not identical to NaN, but only one can be stored in a Set.

The results of

Execution time: 80ms

Memory consumption is 37.5MB

/**
 * @param {string} astr
 * @return {boolean}
 */
var isUnique = function(astr) {
   return new Set([...astr]).size === astr.length
};
Copy the code

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