void nextPermutation(vector<int> &num) {

// Find the largest index i such that num[i-1] < num[i]

int pivot = -1;

for (int i = num.size() - 1; i >= 1; i--) {

if (num[i-1] < num[i]) {

pivot = i - 1;

break;

}

}

if (pivot != -1) {

// Find the largest index j such that j >= i and num[j] > num[i-1]

// Then swap num[j] and num[i-1]

for (int j = num.size() - 1; j > pivot; j--) {

if (num[j] > num[pivot]) {

swap(num[j], num[pivot]);

break;

}

}

}

// Reverse the suffix starting at num[i]

int head = pivot + 1;

int tail = num.size() - 1;

while (head < tail) {

swap(num[head++], num[tail--]);

}

}