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leetCode-393:UTF-8 Validation

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问题描述

给定一个整数数组，要求判断这个是不是utf-8字符。题目链接：**点我**

样例输入输出

输入：[197,130,1]

输出：true

输入：[235,140,4]

输出：false

问题解法

此题直接按照题意描述的规则进行判断即可，代码如下

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class Solution {
    private static final int ONE_BYTE_START = 0;

    private static final int ONE_BYTE_END = 0b01111111;

    private static final int TWO_BYTE_START = 0b11000000;

    private static final int TWO_BYTE_END = 0b11011111;

    private static final int THREE_BYTE_START = 0b11100000;

    private static final int THREE_BYTE_END = 0b11101111;

    private static final int FOUR_BYTE_START = 0b11110000;

    private static final int FOUR_BYTE_END = 0b11110111;

    private static final int FOLLOW_BYTE_START = 0b10000000;

    private static final int FOLLOW_BYTE_END = 0b10111111;

    public boolean validUtf8(int[] data) {
        int i = 0;
        while (i < data.length) {
            int num = data[i];
            if (isFourByte(num)) {
                boolean ok = isFollowByte(data, i + 1) && isFollowByte(data, i + 2) && isFollowByte(data, i + 3);
                if (!ok) {
                    return false;
                }

                i += 4;
                continue;
            }

            if (isThreeByte(num)) {
                boolean ok = isFollowByte(data, i + 1) && isFollowByte(data, i + 2);
                if (!ok) {
                    return false;
                }

                i += 3;
                continue;
            }

            if (isTwoByte(num)) {
                boolean ok = isFollowByte(data, i + 1);
                if (!ok) {
                    return false;
                }

                i += 2;
                continue;
            }

            if (isOneByte(num)) {
                i++;
                continue;
            }

            return false;
        }

        return true;
    }

    private boolean isOneByte(int num) {
        return num >= ONE_BYTE_START && num <= ONE_BYTE_END;
    }

    private boolean isTwoByte(int num) {
        return num >= TWO_BYTE_START && num <= TWO_BYTE_END;
    }

    private boolean isThreeByte(int num) {
        return num >= THREE_BYTE_START && num <= THREE_BYTE_END;
    }

    private boolean isFourByte(int num) {
        return num >= FOUR_BYTE_START && num <= FOUR_BYTE_END;
    }

    private boolean isFollowByte(int[] data, int i) {
        return i < data.length && data[i] >= FOLLOW_BYTE_START && data[i] <= FOLLOW_BYTE_END;
    }
}