Leetcode:Longest Substring Without Repeating Characters 解题报告

Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

public int lengthOfLongestSubstring(String s) {
if (s == null) {
return 0;
}

int max = 0;

// suppose there are only ASCII code.
int[] lastIndex = new int[128];
for (int i = 0; i < 128; i++) {
lastIndex[i] = -1;
}

int len = s.length();
int l = 0;
for (int r = 0; r < len; r++) {
char c = s.charAt(r);

if (lastIndex[c] >= l) {
l = lastIndex[c] + 1;
}

// replace the last index of the character c.
lastIndex[c] = r;

// replace the max value.
max = Math.max(max, r - l + 1);
}

return max;
}

View Code

GITHUB:
https://github.com/yuzhangcmu/LeetCode_algorithm/blob/master/string/LengthOfLongestSubstring.java