392. Is Subsequence

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

.

判断字符串s是否是字符串t的子串，要求顺序不能颠倒。双指针遍历。

class Solution {
public:
bool isSubsequence(string s, string t) {
if(t.size()<s.size())   return false;
if(s.size()==0||t.size()==0) return true;

int indexS = 0;
int indexT = 0;

while(indexT <= t.size()){
if(indexS == s.size()){
return true;
}

if(s[indexS] == t[indexT]){
indexS++;
indexT++;
}else if(s[indexS] != t[indexT]){
indexT++;
}
}

return false;
}
};