longest-substring-palindrom.go

func longestPalindrome(s string) string {
    start, end := 0, 0
    part := 1
    maxPal, maxStart, maxEnd := 0, 0, 0
    lenS := len(s)
    nowBreak := false
    for i:=0;i<lenS;i++ {
        // looping for first try, the even pal
        for {
            if i - part < 0 || i + part >= lenS {
                nowBreak = true
            } else { 
                
                if s[i - part] == s[i + part] {
                    start = i - part
                    end = i + part
                } else {
                    nowBreak = true
                }
            }
            if nowBreak {
                if end - start + 1 > maxPal {
                    maxPal = end - start + 1
                    maxStart = start
                    maxEnd = end
                }
                nowBreak = false // reset it now!
                part = 1
                break
            }
            part = part + 1
        }
        
        // looping for second
        if i+1<lenS && s[i] == s[i+1] {
            // it found 
            start, end = i, i+1
            for {
              
                if i - part < 0 || i + 1 + part >= lenS {
                    nowBreak = true
                } else {                
                    if s[i - part] == s[i + 1 + part] {
                        start = i - part
                        end = i + 1 + part
                    } else {
                        nowBreak = true
                    }
                }
                if nowBreak {
                    if end - start + 1 > maxPal {
                        maxPal = end - start + 1
                        maxStart = start
                        maxEnd = end
                    }
                    nowBreak = false // reset it now!
                    part = 1
                    break
                }
                part = part + 1
            }
        } 
        
    }
    return s[maxStart:maxEnd+1]
}