增加C的贪心算法代码 (#726)

codes/c/CMakeLists.txt

@@ -15,3 +15,4 @@ add_subdirectory(chapter_graph)
 add_subdirectory(chapter_searching)
 add_subdirectory(chapter_sorting)
 add_subdirectory(chapter_backtracking)
+add_subdirectory(chapter_greedy)

codes/c/chapter_greedy/CMakeLists.txt

@@ -0,0 +1 @@
+add_executable(coin_change_greedy coin_change_greedy.c)

codes/c/chapter_greedy/coin_change_greedy.c

@@ -0,0 +1,60 @@
+/**
+ * File: coin_change_greedy.c
+ * Created Time: 2023-09-07
+ * Author: lwbaptx (lwbaptx@gmail.com)
+ */
+
+#include "../utils/common.h"
+
+/* 零钱兑换：贪心 */
+int coinChangeGreedy(int* coins, int size, int amt) {
+    // 假设 coins 列表有序
+    int i = size - 1;
+    int count = 0;
+    // 循环进行贪心选择，直到无剩余金额
+    while (amt > 0) {
+        // 找到小于且最接近剩余金额的硬币
+        while (i > 0 && coins[i] > amt) {
+            i--;
+        }
+        // 选择 coins[i]
+        amt -= coins[i];
+        count++;
+    }
+    // 若未找到可行方案，则返回 -1
+    return amt == 0 ? count : -1;
+}
+
+/* Driver Code */
+int main() {
+    // 贪心：能够保证找到全局最优解
+    int coins1[6] = {1, 5, 10, 20, 50, 100};
+    int amt = 186;
+    int res = coinChangeGreedy(coins1, 6, amt);
+    printf("\ncoins = ");
+    printArray(coins1, 6);
+    printf("amt = %d\n", amt);
+    printf("凑到 %d 所需的最少硬币数量为 %d\n", amt, res);
+
+    // 贪心：无法保证找到全局最优解
+    int coins2[3] = {1, 20, 50};
+    amt = 60;
+    res = coinChangeGreedy(coins2, 3, amt);
+    printf("\ncoins = ");
+    printArray(coins2, 3);
+    printf("amt = %d\n", amt);
+    printf("凑到 %d 所需的最少硬币数量为 %d\n", amt, res);
+    printf("实际上需要的最少数量为 3 ，即 20 + 20 + 20\n");
+
+    // 贪心：无法保证找到全局最优解
+    int coins3[3] = {1, 49, 50};
+    amt = 98;
+    res = coinChangeGreedy(coins3, 3, amt);
+    printf("\ncoins = ");
+    printArray(coins3, 3);
+    printf("amt = %d\n", amt);
+    printf("凑到 %d 所需的最少硬币数量为 %d\n", amt, res);
+    printf("实际上需要的最少数量为 2 ，即 49 + 49\n");
+
+    return 0;
+}