leetcode：2023/4/6

每日一题

1017.负二进制转换

class Solution {
    public String baseNeg2(int n) {
        if(n==0){
            return "0";
        }
        int[] bits=new int[32];
        for(int i=0;i32&&n!=0;i++){
            if((n&1)!=0){
                bits[i]++;
                if((i&1)!=0){
                    bits[i+1]++;
                }
            }
            n>>=1;
        }
        int carry=0;
        for(int i=0;i32;i++){
            int val=carry+bits[i];
            bits[i]=val&1;
            carry=(val-bits[i])/(-2);
        }
        int pos=31;
        StringBuilder res=new StringBuilder();
        while(pos>=0&&bits[pos]==0){
            pos--;
        }
        while(pos>=0){
            res.append(bits[pos]);
            pos--;
        }
        return res.toString();
    }
}

class Solution {
    public String baseNeg2(int n) {
       if(n==0){return "0";}
        String ans="";
        for(int i=0;n>0;i++){
            ans=(n&1)+ans;
            if((i&1)==1){n+=(n&1)1;}
            n>>=1;
        }
        return ans;
    }
}

效率不高

344.翻转字符串

class Solution {
    public void reverseString(char[] s) {
        int n=s.length;
        for(int left=0,right=n-1;leftright;++left,--right){
            char tmp=s[left];
            s[left]=s[right];
            s[right]=tmp;
        }
    }
}

557. 反转字符串中的单词 III

class Solution {
    public String reverseWords(String s) {
        StringBuffer ret = new StringBuffer();
        int length = s.length();
        int i = 0;
        while (i  length) {
            int start = i;
            while (i  length && s.charAt(i) != ' ') {
                i++;
            }
            for (int p = start; p  i; p++) {
                ret.append(s.charAt(start + i - 1 - p));
            }
            while (i  length && s.charAt(i) == ' ') {
                i++;
                ret.append(' ');
            }
        }
        return ret.toString();
    }
}

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