// 946. Validate Stack Sequences #include #include #include /* * given two integer arrays 'pushed' & 'popped' each with distinct * values, return true if this could have been the result of a sequence * of push and pop operations on an initially empty stack, or false otherwise */ bool validateStackSequences(int *pushed, int pushed_size, int *popped, int popped_size) { int i = 0, j = 0, k = 0; int *s = (int *)malloc(pushed_size * sizeof(int)); while (k >= 0 && k < pushed_size && j < popped_size) { if (k > 0 && s[k - 1] == popped[j]) { k--; j++; } else { if (i < pushed_size) { if (pushed[i] == popped[j]) { i++; j++; } else s[k++] = pushed[i++]; } else { free(s); return false; } } } free(s); return true; } int main() { int pushed[] = {1, 2, 3, 4, 5}; int p1[] = {4, 5, 3, 2, 1}, p2[] = {4, 3, 5, 1, 2}; printf("%d\n", validateStackSequences(pushed, 5, p1, 5)); // expect: 1 printf("%d\n", validateStackSequences(pushed, 5, p2, 5)); // expect: 0 }