leetcode day3

剑指 Offer 05. 替换空格

思路：java的replace()函数

return s.replace(" ","%20");

剑指 Offer 58 - II. 左旋转字符串

思路：java的subSring()函数。public String substring(int beginIndex)

该子字符串始于指定索引处的字符，一直到此字符串末尾

public String reverseLeftWords(String s, int n) {
        String s1 = s.substring(0,n);
        String s2 = s.substring(n,s.length());
        return s2+s1;
    }