题目：

题解：

bool canFinish(int numCourses, int** prerequisites, int prerequisitesSize, int* prerequisitesColSize) {int** edges = (int**)malloc(sizeof(int*) * numCourses);for (int i = 0; i < numCourses; i++) {edges[i] = (int*)malloc(0);}int edgeColSize[numCourses];memset(edgeColSize, 0, sizeof(edgeColSize));int indeg[numCourses];memset(indeg, 0, sizeof(indeg));for (int i = 0; i < prerequisitesSize; ++i) {int a = prerequisites[i][1], b = prerequisites[i][0];edgeColSize[a]++;edges[a] = (int*)realloc(edges[a], sizeof(int) * edgeColSize[a]);edges[a][edgeColSize[a] - 1] = b;++indeg[b];}int q[numCourses];int l = 0, r = -1;for (int i = 0; i < numCourses; ++i) {if (indeg[i] == 0) {q[++r] = i;}}int visited = 0;while (l <= r) {++visited;int u = q[l++];for (int i = 0; i < edgeColSize[u]; ++i) {--indeg[edges[u][i]];if (indeg[edges[u][i]] == 0) {q[++r] = edges[u][i];}}}for (int i = 0; i < numCourses; i++) {free(edges[i]);}free(edges);return visited == numCourses;
}