min stack

Author: specialtactics

week2/min-stack.c

@@ -0,0 +1,111 @@
+typedef struct {
+ int value;
+ void *prev;
+} El;
+
+typedef struct {
+ El *top;
+ int min;
+} MinStack;
+
+/** initialize your data structure here. */
+MinStack* minStackCreate() {
+ MinStack* new = malloc(sizeof(MinStack));
+ 
+ new->top = NULL;
+ new->min = 0; // If stack has no elements
+ 
+ return new;
+}
+
+void minStackPush(MinStack* obj, int x) {
+ // Push
+ El* new = malloc(sizeof(El));
+ new->value = x;
+ 
+ // First element
+ if (obj->top == NULL) {
+ new->prev = NULL;
+ obj->min = x;
+ }
+ // Other elements
+ else {
+ new->prev = obj->top;
+ 
+ // Handle min caching
+ if (x < obj->min) {
+ obj->min = x;
+ }
+ }
+ 
+ obj->top = new;
+}
+
+void minStackPop(MinStack* obj) {
+ if (obj->top != NULL) {
+ El *toRemove = obj->top;
+ obj->top = toRemove->prev;
+ 
+ // Recalculate minimum if needed
+ if (toRemove->value == obj->min) {
+ recalculateMin(obj);
+ }
+ 
+ free(toRemove);
+ }
+}
+
+int minStackTop(MinStack* obj) {
+ return obj->top->value;
+}
+
+int minStackGetMin(MinStack* obj) {
+ return obj->min;
+}
+
+void minStackFree(MinStack* obj) {
+ El *remove, *next = obj->top;
+ 
+ while (next != NULL) {
+ remove = next;
+ next = next->prev;
+ 
+ free(remove);
+ }
+ 
+ free(obj);
+}
+
+void recalculateMin(MinStack* obj) {
+ El *next = obj->top;
+ int min = 0;
+ 
+ if (next != NULL) {
+ min = next->value;
+ next = next->prev;
+ 
+ while (next != NULL) {
+ if (next->value < min) {
+ min = next->value;
+ }
+ next = next->prev;
+ }
+ }
+ 
+ obj->min = min;
+}
+
+
+/**
+ * Your MinStack struct will be instantiated and called as such:
+ * MinStack* obj = minStackCreate();
+ * minStackPush(obj, x);
+ 
+ * minStackPop(obj);
+ 
+ * int param_3 = minStackTop(obj);
+ 
+ * int param_4 = minStackGetMin(obj);
+ 
+ * minStackFree(obj);
+*/