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56 lines
1.8 KiB
JavaScript
56 lines
1.8 KiB
JavaScript
function successor(str) {
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var alphabet = 'abcdefghijklmnopqrstuvwxyz',
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length = alphabet.length,
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result = str,
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i = str.length;
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while(i >= 0) {
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var last = str.charAt(--i),
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next = '',
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carry = false;
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if (isNaN(last)) {
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index = alphabet.indexOf(last.toLowerCase());
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if (index === -1) {
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next = last;
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carry = true;
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}
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else {
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var isUpperCase = last === last.toUpperCase();
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next = alphabet.charAt((index + 1) % length);
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if (isUpperCase) {
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next = next.toUpperCase();
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}
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carry = index + 1 >= length;
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if (carry && i === 0) {
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var added = isUpperCase ? 'A' : 'a';
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result = added + next + result.slice(1);
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break;
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}
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}
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}
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else {
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next = +last + 1;
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if(next > 9) {
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next = 0;
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carry = true;
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}
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if (carry && i === 0) {
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result = '1' + next + result.slice(1);
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break;
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}
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}
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result = result.slice(0, i) + next + result.slice(i + 1);
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if (!carry) {
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break;
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}
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}
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return result;
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}
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console.log(successor('abcd'));
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console.log(successor('3456'));
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