4351: GESP C++ 四级 4图像压缩202306

#include <iostream>
#include <cstring>
using namespace std;

int image[20][20];
int cpimg[20][20];
int his[256];
int color[16];
// 一位十六进制字符转换为数字
int trans(char a) {
    if (a <= '9')
        return (a - '0');
    return (a - 'A' + 10);
}
// 一位十六进制数字转换为字符
char itrans(int n) {
    if (n >= 10)
        return (char)(n - 10 + 'A');
    return (char)(n + '0');
}
// 寻找离 c 最近的灰阶
int compress(int c) {
    int dis = 256, res = -1;
    for (int i = 0; i < 16; i++) {
        int d = c - color[i];
        if (d < 0)
            d = -d;
        if (d < dis) {
            dis = d;
            res = i;
        }
    }
    return res;
}
int main() {
    int N = 0, M = 0;
    cin >> N;
    // 灰阶计数，初始化为-1
    for (int i = 0; i < 256; i++)
    his[i] = -1;
    // 输入图像，并对灰阶计数
    for (int i = 0; i < N; i++) {
        char line[50];
        cin >> line;
        M = strlen(line) / 2;
        for (int j = 0; j < M; j++) {
            int c = trans(line[j * 2]) * 16 + trans(line[j * 2 + 1]);
            image[i][j] = c;
            his[c]++;
        }
    }
    // 选取出现次数最多的 16 个灰阶
    for (int c = 0; c < 16; c++) {
        int max = 0, max_id = -1;
        for (int i = 0; i < 256; i++)
        if (his[i] > max) {
            max = his[i];
            max_id = i;
        }
        color[c] = max_id;
        his[max_id] = -1;
    }
    // 将 image 的灰阶压缩为 cpimg
    for (int i = 0; i < N; i++)
        for (int j = 0; j < M; j++)
            cpimg[i][j] = compress(image[i][j]);
    // 输出选取的 16 个灰阶
    for (int c = 0; c < 16; c++)
        cout << itrans(color[c] / 16) << itrans(color[c] % 16);
    cout << endl;
    // 输出压缩后的图像
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < M; j++)
            cout << itrans(cpimg[i][j]);
        cout << endl;
    }
    return 0;
}