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DS/C/Lab/Week4/fasttranspose.c

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+#include <stdio.h>
+
+#define MAX_TERMS 100
+#define MAX_COL 100
+
+struct Element {
+    int row, col, value;
+};
+
+void fastTranspose(struct Element *a, struct Element *b, int m, int n, int num) {
+    int rowTerms[MAX_COL] = {0};
+    int rowStart[MAX_COL] = {0};
+    int i, j;
+
+    for (i = 0; i < num; i++)
+        rowTerms[a[i].col]++;
+
+    for (i = 1; i < n; i++)
+        rowStart[i] = rowStart[i-1] + rowTerms[i-1];
+
+    for (i = 0; i < num; i++) {
+        j = rowStart[a[i].col]++;
+        b[j].row = a[i].col;
+        b[j].col = a[i].row;
+        b[j].value = a[i].value;
+    }
+}
+
+int main() {
+    struct Element a[MAX_TERMS] = {{0, 1, 3}, {1, 2, 5}, {2, 0, 2}, {3, 1, 4}};
+    struct Element b[MAX_TERMS];
+    int m = 4, n = 3, num = 4;
+
+    fastTranspose(a, b, m, n, num);
+
+    for (int i = 0; i < num; i++)
+        printf("%d %d %d\n", b[i].row, b[i].col, b[i].value);
+
+    return 0;
+}