1、无重复字符的最长子串—*
给定一个字符串，请你找出其中不含有重复字符的 最长子串 的长度。
var lengthOfLongestSubstring = function (s) {
let max = 0;
let frompos = 0;
for (let i = 0; i < s.length; i++) {
let pos = s.indexOf(s[i], frompos);
if(pos > -1 && pos < i ) frompos = pos + 1;
max = Math.max(max, i - frompos + 1);
}
return max;
};
var lengthOfLongestSubstring = function(s) {
let substr = '', maxLength = 0;
// find the next substring that longeer than previous to replace previous substring
for (var i = 0; i < s.length; i++) {
let findIndex = substr.indexOf(s[i]);
if (~findIndex) {
substr = substr.substring(findIndex + 1);
}
substr += s[i];
if (substr.length > maxLength) {
maxLength = substr.length;
}
}
return maxLength;
};
let lengthOfLongestSubstring = function(s) {
let map = new Map();
let max = 0;
for (let i = 0, j = 0; i < s.length && j < s.length; ++i) {
let pos = map.get(s[i]);
if (pos !== undefined) {
j = Math.max(pos + 1, j);
}
max = Math.max(max, i - j + 1);
map.set(s[i], i);
}
return max;
};
2、最长公共前缀—*
编写一个函数来查找字符串数组中的最长公共前缀。如果不存在公共前缀，返回空字符串
""。
var longestCommonPrefix = function (strs) {
let res = '';
const tmp = strs[0] || '';
let preModel = tmp.slice(0, 1);
let cur = 1;
const len = strs.length;
if(len === 1) return tmp;
while(cur <= tmp.length) {
for(let i = 1; i < len; i++) {
if(strs[i].indexOf(preModel) !== 0) return res;
}
res = preModel;
preModel = tmp.slice(0, cur +1);
cur++;
}
return res;
};
var longestCommonPrefix = function (strs) {
let str = '';
if (strs.length == 0) return str;
let minL = strs[0].length;
strs.forEach(item => {
if (item.length < minL) {
minL = item.length
}
})
for (let i = minL; i > 0; i--) {
let _str = strs[0].substr(0, i)
let key = true;
for (let j = 0; j < strs.length; j++) {
let _strs = strs[j].substr(0, i)
if (_strs != _str) {
key = false;
break;
}
}
if (key) {
str = _str;
break
}
}
return str;
};
var longestCommonPrefix = function(strs) {
let prefix = ""
if(strs.length <=0){
return prefix
}
let minLength = strs[0].length
for(let i=1;i3、字符串的排列
给定两个字符串 s1 和 s2，写一个函数来判断 s2 是否包含 s1 的排列。
var isSameInOrder = function(s1, s2) {
const order2 = s2.split('').sort().join('');
return s1 === order2;
}
var checkInclusion = function (s1, s2) {
const len1 = s1.length;
const len2 = s2.length;
if(len1 > len2) return false;
const dislen = len2 - len1;
const orders1 = s1.split('').sort().join('');
for(let i = 0; i <= dislen; i++) {
const substr = s2.substr(i, len1);
if(isSameInOrder(orders1, substr)) return true;
}
return false;
};
const checkInclusion1 = function (s1, s2) {
const count1 = Array(26).fill(0)
const count2 = Array(26).fill(0)
for (let i = 0; i < s1.length; i++) {
count1[s1.charCodeAt(i) - 97]++
count2[s2.charCodeAt(i) - 97]++
}
if (isSame(count1, count2)) {
return true
}
for (let i = s1.length; i < s2.length; i++) {
count2[s2.charCodeAt(i - s1.length) - 97]-- // 匹配串往后移一位
count2[s2.charCodeAt(i) - 97]++
if (isSame(count1, count2)) {
return true
}
}
return false
}
const isSame = (arr1, arr2) => {
if (arr1.length !== arr2.length) {
return false
}
for (let i = 0; i < arr1.length; i++) {
if (arr1[i] !== arr2[i]) return false
}
return true
}
4、字符串相乘
给定两个以字符串形式表示的非负整数
num1和num2，返回num1和num2的乘积，它们的乘积也表示为字符串形式。
var multiply = function(num1, num2) {
if(num1 === '0' || num2 === '0') return '0';
const len1 = num1.length;
const len2 = num2.length;
if(len1 > len2) {
[num1, num2] = [num2, num1];
}
const arr1 = num1.split('');
const arr2 = num2.split('');
const tmp = {}; // 缓存计算过内容
tmp['0'] = '0';
tmp['1'] = num2;
let mul = 1;
for(var i = num1.length - 1; i >=0 ; i--) {
mul
}
};
5、翻转字符串里的单词
给定一个字符串，逐个翻转字符串中的每个单词。
var reverseWords = function(str) {
const arr = str.replace(/(^\s*)|(\s*$)/g, '').replace(/\s+/g, ' ').split(' ');
return arr.reverse().join(' ');
// return str.trim().replace(/\s+/g, ' ').split(' ').reverse().join(' ');
};
let reverseWords = function(str) {
let s = "";
let c = "";
for (let i = str.length - 1; i >= 0; --i) {
if (c !== "" && str[i] === " ") {
s += " " + c;
c = "";
}
if (str[i] !== " ") {
c = str[i] + c;
}
}
if (c !== "") {
s += " " + c;
}
return s.length > 0 ? s.substring(1) : "";
};
6、简化路径—*
输入："/a/./b/../../c/" 输出："/c"
var simplifyPath = function (path) {
const dirArr = path.split('/');
const curPath = [];
for (let i = 0; i < dirArr.length; i++) {
const cur = dirArr[i];
if (cur === '..') {
curPath.pop();
} else if (cur === '.' || !cur) {
} else {
curPath.push(cur);
}
}
return `/${curPath.join('/')}`;
};
var simplifyPath = function(path) {
let arr = path.split('/');
let res = [];
for (let p of arr) {
if (p === '..') {
res.pop();
} else if (p !== '' && p !== '.') {
res.push(p);
}
}
return '/' + res.join('/');
};
7、复原IP地址—*
给定一个只包含数字的字符串，复原它并返回所有可能的 IP 地址格式。
var restoreIpAddresses = function(s) {
const len = s.length;
const res = [];
if(len < 4 || len > 12) return res;
splitStr(s, '', res, 0);
return res;
};
function splitStr(str, last, res, count) {
if (count === 3 && isValid(str)) {
res.push(`${last}${str}`);
return;
}
for(let i = 1; i < 4 && i < str.length; i++) {
let curStr = str.substr(0, i);
if(isValid(curStr)) {
splitStr(str.substr(i), `${last}${curStr}.`, res, count + 1);
}
}
}
function isValid(num) {
if (num[0] === '0') return num === '0';
return num <= 255 && num >= 0;
}
let restoreIpAddresses = function(s) {
let res = [];
helper(s, 0, 4, res, []);
return res;
};
let helper = function(s, pos, parts, res, current) {
if (parts === 0 && pos === s.length) {
res.push(current.slice().join('.'));
} else if (parts === 0 || pos === s.length) {
return;
} else {
let pre = 0;
for (let i = pos; i < s.length && (i === pos || pre > 0); ++i) {
let val = pre * 10 + parseInt(s[i]);
pre = val;
if (val <= 255) {
current.push(val);
helper(s, i + 1, parts - 1, res, current);
current.pop();
} else {
break;
}
}
}
};