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;
}