119 lines
2.2 KiB
C
119 lines
2.2 KiB
C
#include <stdio.h>
|
|
|
|
int hoare(int* arr, int i, int j, int idx) {
|
|
printf("I: %d, J: %d, IDX: %d\n", i, j, idx);
|
|
if (idx < i) {
|
|
return 0xdeadbeef;
|
|
}
|
|
|
|
if (idx > j) {
|
|
return 0xdeadbeef;
|
|
}
|
|
|
|
int v;
|
|
int x1,x2;
|
|
int t;
|
|
while (i < j - 1) {
|
|
v = arr[(i + j) / 2];
|
|
printf("Round: (%d,%d) - v: %d\n", i, j, v);
|
|
// sorting on three partitions
|
|
|
|
x1 = i;
|
|
x2 = j;
|
|
|
|
while (x1 < x2) {
|
|
|
|
while (x1 < x2 && arr[x1] <= v) {
|
|
printf("x1: %d, arr[x1]: %d\n", x1, arr[x1]);
|
|
x1++;
|
|
}
|
|
|
|
while (x1 < x2 && arr[x2] > v) {
|
|
printf("x2: %d, arr[x2]: %d\n", x2, arr[x2]);
|
|
x2--;
|
|
}
|
|
|
|
printf("X1 %d to swap %d\n", x1, arr[x1]);
|
|
printf("X2 %d to swap %d\n", x2, arr[x2]);
|
|
|
|
// if x1 == x2, the change makes no difference
|
|
|
|
t = arr[x1];
|
|
arr[x1] = arr[x2];
|
|
arr[x2] = t;
|
|
|
|
}
|
|
|
|
if (arr[x1] > v) x1--; // we could cross == element by
|
|
|
|
x2 = x1;
|
|
x1 = i;
|
|
|
|
while (x1 < x2) {
|
|
|
|
while (x1 < x2 && arr[x1] < v) {
|
|
printf("x1: %d, arr[x1]: %d\n", x1, arr[x1]);
|
|
x1++;
|
|
}
|
|
|
|
while (x1 < x2 && arr[x2] == v) {
|
|
printf("x2: %d, arr[x2]: %d\n", x2, arr[x2]);
|
|
x2--;
|
|
}
|
|
|
|
printf("X1 %d to swap %d\n", x1, arr[x1]);
|
|
printf("X2 %d to swap %d\n", x2, arr[x2]);
|
|
|
|
// if x1 == x2, the change makes no difference
|
|
|
|
t = arr[x1];
|
|
arr[x1] = arr[x2];
|
|
arr[x2] = t;
|
|
|
|
}
|
|
|
|
if (x1 > idx) {
|
|
printf("Changing j %d to %d\n", j, x1);
|
|
j = x1;
|
|
} else {
|
|
// x1 <= idx
|
|
printf("Changing i %d to %d\n", i, x1);
|
|
i = x1;
|
|
}
|
|
}
|
|
|
|
// we should have i == j == idx
|
|
printf("i: %d, j: %d, idx: %d, v: %d\n", i, j, idx, arr[idx]);
|
|
return arr[idx]; // in order to make it work, we need to make sure that in this place is fully sorted, one way is to split into three pieces
|
|
}
|
|
|
|
/**
|
|
* n: 4
|
|
* 4
|
|
* 3
|
|
* 2
|
|
* 1
|
|
* idx: 4, 3, 2, 1 all work
|
|
*/
|
|
|
|
int main() {
|
|
|
|
int n;
|
|
printf("Provide n: ");
|
|
scanf("%d", &n);
|
|
|
|
int numbers[n];
|
|
|
|
for (int i = 0; i < n; i++) {
|
|
scanf("%d", &numbers[i]);
|
|
}
|
|
|
|
int idx;
|
|
printf("Idx: ");
|
|
scanf("%d", &idx);
|
|
|
|
int res = hoare(numbers, 0, n-1, idx);
|
|
printf("Res: %x\n", res);
|
|
return 0;
|
|
}
|