add prob4

4-11-container-with-most-water.c

@@ -0,0 +1,75 @@
+#include <bits/stdc++.h>
+
+struct heightpair {
+    int height;
+    int x;
+};
+
+void swap(struct heightpair *a, struct heightpair *b) {
+    struct heightpair tmp = *a;
+    *a = *b;
+    *b = tmp;
+}
+
+void quicksort(struct heightpair *a, int le, int ri) {
+    int i = le, j = ri - 1;
+    struct heightpair pivot = a[(rand() %(ri - le)) + le];
+    // printf("le = %d, ri = %d, pivot.height = %d\n", le, ri, pivot.height);
+    // for (int i = le; i < ri; i++) {
+    //     printf("%d\n", a[i]);
+    // }
+    while (i <= j) {
+        while (a[i].height > pivot.height) i++;
+        while (a[j].height < pivot.height) j--;
+        // printf("i = %d, j = %d\n", i, j);
+        if (i <= j) swap(&a[i++], &a[j--]);
+    }
+
+    // for (int i = le; i < ri; i++) {
+    //     printf("%d\n", a[i]);
+    // }
+    // printf("----\n");
+
+    if (le < j) quicksort(a, le, j + 1);
+    if (i < ri - 1) quicksort(a, i, ri);
+}
+
+int maxArea(int *height, int heightSize) {
+    struct heightpair *pairs = (struct heightpair *)malloc(heightSize * sizeof(struct heightpair));
+    for (int i = 0; i < heightSize; i++) {
+        pairs[i].height = height[i];
+        pairs[i].x = i;
+    }
+    quicksort(pairs, 0, heightSize);
+    // for (int i = 0; i < heightSize; i++) {
+    //     printf("%d, %d\n", pairs[i].height, pairs[i].x);
+    // }
+    struct heightpair curleft = pairs[0];
+    struct heightpair curright = pairs[0];
+    int curmax = 0;
+    for (int i = 1; i < heightSize; i++) {
+        if (pairs[i].x < curleft.x) {
+            int vol = (curright.x - pairs[i].x) * pairs[i].height;
+            curmax = curmax > vol ? curmax : vol;
+            curleft = pairs[i];
+        }
+        else if (pairs[i].x < curright.x) {
+            int vol1 = (pairs[i].x - curleft.x) * pairs[i].height;
+            int vol2 = (curright.x - pairs[i].x) * pairs[i].height;
+            curmax = curmax > vol1 ? curmax : vol1;
+            curmax = curmax > vol2 ? curmax : vol2;
+        } else {
+            // pairs[i].x > curright.x
+            int vol = (pairs[i].x - curleft.x) * pairs[i].height;
+            curmax = curmax > vol ? curmax : vol;
+            curright = pairs[i];
+        }
+    }
+    return curmax;
+}
+
+int main() {
+    int nums[] = {1,8,6,2,5,4,8,3,7};
+    printf("%d\n", maxArea(nums, sizeof(nums) / sizeof(int)));
+    return 0;
+}