標(biāo)簽： DP
Given a string, find the length of the longest substring without repeating characters.
Examples:
Given "abcabcbb", the answer is "abc", which the length is 3.
Given "bbbbb", the answer is "b", with the length of 1.
Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.
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有點(diǎn)像回文串，f[i] 表示以 i 結(jié)尾的子串最長(zhǎng)匹配括號(hào)，轉(zhuǎn)移方程是：
f[i] = 2 + f[i-1] if s[i] = ‘)’ and s[i-f[i-1]-1]=’(’+ f[i-f[i]]
| ( | ( | ) | ( | ) | ) | ( | ) |
|---|---|---|---|---|---|---|---|
| 0 | 0 | 2 | 0 | 4 | 6 | 0 | 8 |
class Solution {
public:
int lengthOfLongestSubstring(string s) {
int pos[256];
for(int index = 0; index < 256; index++){
pos[index] = -1;
}
int start = 0;
int ret = 0;
for(int index = 0; index < s.length(); index++){
if(pos[s[index]] >= start){
start = pos[s[index]] + 1;
}
pos[s[index]] = index;
ret = max(ret, index - start + 1);
}
return ret;
}
};
