Description
Given a string s and a string t, check if s is subsequence of t.
You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100).
A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (ie, “ace” is a subsequence of “abcde” while “aec” is not).
Example 1:
s = “abc”, t = “ahbgdc”
Return true.
Example 2:
s = “axc”, t = “ahbgdc”
Return false.
My program:
从s和t的首端开始遍历比较字符是否相等即可，如果不等，则增加在t中的下标j位置；如果相等，则同时增加s中下标i和t中下标j。如果t中的指标位置增长到了t的末尾，而s中的指标还没有增长的末尾，则返回false。如果s中的指标先增长到了末尾，则返回true。
class Solution {
public:
bool isSubsequence(string s, string t) {
int i = 0, j = 0;
if (s.empty()) return true;
while(i<s.size() && j<t.size())
{
if(s[i] == t[j])
{
++i;
++j;
}
else
++j;
}
if (i<s.size()) return false;
else return true;
}
};Simple C++ code:
bool isSubsequence(string s, string t) {
int si= 0;
for(int ti = 0; ti < t.size() && si < s.size(); ti++) {
if(t[ti] == s[si]) si++;
}
return si == s.size();
}