c语言编写程序根据二叉树中序遍历的非递归算法，在二叉树t查找值为x的元素，若找到且其左子树为空，则将值为y的元素插入成为其左孩子，否则若其右孩子为空，则将y插入成为其右孩子。插入失败，返回值为0，否则返回值为1。

好的，以下是用C语言实现上述算法的代码：

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

// 定义二叉树节点结构体
typedef struct TreeNode {
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
} TreeNode;

// 定义栈结构体
typedef struct Stack {
    int top;
    int capacity;
    TreeNode** array;
} Stack;

// 初始化栈
Stack* createStack(int capacity) {
    Stack* stack = (Stack*) malloc(sizeof(Stack));
    stack->top = -1;
    stack->capacity = capacity;
    stack->array = (TreeNode**) malloc(stack->capacity * sizeof(TreeNode*));
    return stack;
}

// 判断栈是否为空
bool isEmpty(Stack* stack) {
    return stack->top == -1;
}

// 判断栈是否已满
bool isFull(Stack* stack) {
    return stack->top == stack->capacity - 1;
}

// 入栈
void push(Stack* stack, TreeNode* node) {
    if (isFull(stack)) {
        return;
    }
    stack->array[++stack->top] = node;
}

// 出栈
TreeNode* pop(Stack* stack) {
    if (isEmpty(stack)) {
        return NULL;
    }
    return stack->array[stack->top--];
}

// 非递归中序遍历二叉树
bool inorderTraversal(TreeNode* root, int x, int y) {
    Stack* stack = createStack(100);
    TreeNode* current = root;
    bool flag = false; // 标记是否找到目标节点
    while (current != NULL || !isEmpty(stack)) {
        while (current != NULL) {
            push(stack, current);
            current = current->left;
        }
        current = pop(stack);
        if (current->val == x) { // 找到目标节点
            if (current->left == NULL) { // 左子树为空，插入y作为左孩子
                TreeNode* node = (TreeNode*) malloc(sizeof(TreeNode));
                node->val = y;
                node->left = NULL;
                node->right = NULL;
                current->left = node;
                flag = true;
            } else if (current->right == NULL) { // 右子树为空，插入y作为右孩子
                TreeNode* node = (TreeNode*) malloc(sizeof(TreeNode));
                node->val = y;
                node->left = NULL;
                node->right = NULL;
                current->right = node;
                flag = true;
            }
            break;
        }
        current = current->right;
    }
    return flag;
}

int main() {
    // 构造二叉树
    TreeNode* t = (TreeNode*) malloc(sizeof(TreeNode));
    t->val = 5;
    t->left = (TreeNode*) malloc(sizeof(TreeNode));
    t->left->val = 3;
    t->left->left = (TreeNode*) malloc(sizeof(TreeNode));
    t->left->left->val = 2;
    t->left->left->left = NULL;
    t->left->left->right = NULL;
    t->left->right = (TreeNode*) malloc(sizeof(TreeNode));
    t->left->right->val = 4;
    t->left->right->left = NULL;
    t->left->right->right = NULL;
    t->right = (TreeNode*) malloc(sizeof(TreeNode));
    t->right->val = 7;
    t->right->left = (TreeNode*) malloc(sizeof(TreeNode));
    t->right->left->val = 6;
    t->right->left->left = NULL;
    t->right->left->right = NULL;
    t->right->right = (TreeNode*) malloc(sizeof(TreeNode));
    t->right->right->val = 8;
    t->right->right->left = NULL;
    t->right->right->right = NULL;

    // 测试插入操作
    int x = 2, y = 1;
    bool result = inorderTraversal(t, x, y);
    if (result) {
        printf("插入成功！\n");
    } else {
        printf("插入失败！\n");
    }
    return 0;
}

以上代码中，我们首先定义了二叉树节点结构体和栈结构体，并实现了栈的基本操作。然后，我们使用非递归方式实现了中序遍历二叉树，并在遍历过程中进行节点查找和插入操作。最后，我们通过构造的二叉树和目标值x、插入值y进行了测试。