leetcode:Is Subsequence
阿新 • • 發佈:2018-12-24
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"
Example 1:
s = "abc", t = "ahbgdc"
Return true
.
Example 2:
s = "axc", t = "ahbgdc"
Return false
.
直接從s和t的首端開始遍歷比較字元是否相等即可,如果不等,則增加在t中的下標位置;如果相等,則同時增加在s和t中的下標位置。如果t中的指標位置增長到了t的末尾,而s中的指標還沒有增長的末尾,則返回false。如果s中的指標先增長到了末尾,則返回true。
程式碼:
bool isSubsequence(string s, string t) {int i, j, last = 0;
for (i = 0; i < s.size(); i++) {
for (j = last; j < t.size(); j++) {
if (s[i] == t[j]) {
last = j + 1;
break;
}
}
if (j == t.size()) return false;
}
return true;
}