题目：

题解：

int cmp(int** a, int** b) {
    return (*a)[0] == (*b)[0] ? (*b)[1] - (*a)[1] : (*a)[0] - (*b)[0];
}

int maxEnvelopes(int** envelopes, int envelopesSize, int* envelopesColSize) {
    if (envelopesSize == 0) {
        return 0;
    }

    qsort(envelopes, envelopesSize, sizeof(int*), cmp);

    int n = envelopesSize;
    int f[n];
    for (int i = 0; i < n; i++) {
        f[i] = 1;
    }
    int ret = 1;
    for (int i = 1; i < n; ++i) {
        for (int j = 0; j < i; ++j) {
            if (envelopes[j][1] < envelopes[i][1]) {
                f[i] = fmax(f[i], f[j] + 1);
            }
        }
        ret = fmax(ret, f[i]);
    }
    return ret;
}